diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index 5477215..f023f74 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -34,6 +34,7 @@ jobs:
           r-version: ${{ matrix.config.r }}
           http-user-agent: ${{ matrix.config.http-user-agent }}
           use-public-rspm: true
+          extra-repositories: 'https://bnprks.r-universe.dev'
 
       - uses: r-lib/actions/setup-r-dependencies@v2
         with:
diff --git a/DESCRIPTION b/DESCRIPTION
index 17830e9..5a6b958 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -17,7 +17,8 @@ RoxygenNote: 7.3.2
 Suggests: 
     testthat (>= 3.0.0),
     Matrix,
-    SeuratObject (>= 5.0.0)
+    SeuratObject (>= 5.0.0),
+    BPCells
 Config/testthat/edition: 3
 Imports:
     methods,
diff --git a/R/hdf5.R b/R/hdf5.R
index 9a568d0..4ca879f 100644
--- a/R/hdf5.R
+++ b/R/hdf5.R
@@ -25,11 +25,14 @@ create_hdf5 <- function(
   if (file.exists(h5path)) {
     return(err(sprintf("cannot create h5 file as it already exists: %s", h5path)))
   }
-
-  # create hdf5 file and matrix groups
-  f <- hdf5r::H5File$new(h5path, mode = "w")
-
-  write_mat(f, count_mat, feature_ids)
+  if (inherits(count_mat, "IterableMatrix")) {
+    write_mat_bpcells(h5path, count_mat, feature_ids)
+    f <- hdf5r::H5File$new(h5path, mode = "r+")
+  } else {
+    # create hdf5 file and matrix groups
+    f <- hdf5r::H5File$new(h5path, mode = "w")
+    write_mat(f, count_mat, feature_ids)
+  }
   write_clusters(f, clusters)
   write_projections(f, projections)
   write_metadata(f, seurat_obj_version)
@@ -79,6 +82,56 @@ write_mat <- function(f, count_mat, feature_ids) {
   features_group$close()
 }
 
+#' Writes BPCells matrix to the H5 file
+#'
+#' @param h5path Path to a new H5 file
+#' @param count_mat A sparse matrix inheriting from \code{IterableMatrix} from \pkg{BPCells}.
+#'   Rows are features, Columns are barcodes.
+#' @param feature_ids optional character vector that specifies the feature ids of the count matrix.
+#'   Typically, these are the ensemble ids.
+#'
+#' @note
+#' This function will check whether \pkg{BPCells} is installed.
+#'
+#' @noRd
+write_mat_bpcells <- function(h5path, count_mat, feature_ids) {
+  if (!requireNamespace("BPCells", quietly = TRUE)) {
+    stop(
+      "Please install 'BPCells' to write IterableMatrix:\n",
+      " remotes::install_github('bnprks/BPCells/r')"
+    )
+  }
+  features <- rownames(count_mat)
+  barcodes <- colnames(count_mat)
+  if (length(feature_ids) == 0) {
+    feature_ids <- rownames(count_mat)
+  }
+  if (!BPCells::matrix_type(count_mat) == "uint32_t") {
+    count_mat <- BPCells::convert_matrix_type(count_mat)
+  }
+  count_mat <- BPCells::write_matrix_10x_hdf5(count_mat, path = h5path)
+
+  # Need to rewrite the barcodes and features to use strings with max length
+  f <- hdf5r::H5File$new(h5path, mode = "r+")
+
+  matrix_group <- f$open("matrix")
+  hdf5r::h5unlink(matrix_group, "features")
+  hdf5r::h5unlink(matrix_group, "barcodes")
+
+  create_str_dataset(matrix_group, "barcodes", barcodes)
+  features_group <- matrix_group$create_group("features")
+
+  create_str_dataset(features_group, "name", features)
+  create_str_dataset(features_group, "id", as.character(feature_ids))
+  create_str_dataset(features_group, "feature_type", rep("Gene Expression", length(features)))
+  create_str_dataset(features_group, "_all_tag_keys", as.character()) # required features
+  features_group$close()
+  matrix_group$close()
+
+  f$close_all() # make sure everything closed
+}
+
+
 #' Prints the metadata list to stdout.
 #'
 #' @param metadata The metadata list
diff --git a/R/validate.R b/R/validate.R
index 735d461..ea6fe99 100644
--- a/R/validate.R
+++ b/R/validate.R
@@ -15,8 +15,8 @@
 #'
 #' @export
 validate_count_mat <- function(count_mat, feature_ids = NULL) { # nolint: cyclocomp_linter.
-  if (!is(count_mat, "dgCMatrix")) {
-    return(err("count_mat must be a dgCMatrix"))
+  if (!is(count_mat, "dgCMatrix") && !inherits(count_mat, "IterableMatrix")) {
+    return(err("count_mat must be a dgCMatrix or IterableMatrix"))
   }
 
   features <- rownames(count_mat)
@@ -34,11 +34,13 @@ validate_count_mat <- function(count_mat, feature_ids = NULL) { # nolint: cycloc
   if (length(barcodes) == 0) {
     return(err("count_mat must have at least one barcode"))
   }
-  if (any(is.nan(count_mat@x))) {
-    return(err("matrix values must not be NaN"))
-  }
-  if (any(is.infinite(count_mat@x))) {
-    return(err("matrix values must not be infinite"))
+  if (inherits(count_mat, "dgCMatrix")) {
+    if (any(is.nan(count_mat@x))) {
+      return(err("matrix values must not be NaN"))
+    }
+    if (any(is.infinite(count_mat@x))) {
+      return(err("matrix values must not be infinite"))
+    }
   }
   if (!all(sapply(barcodes, nzchar))) {
     return(err("barcodes cannot be the empty string"))
diff --git a/tests/testthat/helper.R b/tests/testthat/helper.R
index d678ebb..eacf0c8 100644
--- a/tests/testthat/helper.R
+++ b/tests/testthat/helper.R
@@ -27,6 +27,32 @@ create_count_mat <- function(rows, cols, valid_barcodes = FALSE) {
   mat
 }
 
+#' Create a sparse count_mat with BPCells
+#'
+#' @importFrom Matrix rsparsematrix
+create_count_mat_bpcells <- function(rows, cols, valid_barcodes = FALSE) {
+  mat <- Matrix::rsparsematrix(rows, cols, 0.5, rand.x = function(n) as.integer(100 * runif(n)))
+
+  rownames <- as.character()
+  if (rows > 0) {
+    rownames <- paste0("row", 1:rows)
+  }
+
+  colnames <- as.character()
+  if (cols > 0) {
+    if (valid_barcodes) {
+      colnames <- lapply(rep(14, cols), random_barcode)
+    } else {
+      colnames <- paste0("col", 1:cols)
+    }
+  }
+
+  dimnames(mat) <- list(rownames, colnames)
+
+  mat_dir <- tempfile(pattern = "bpcells")
+  BPCells::write_matrix_dir(mat, mat_dir)
+}
+
 #' Create a dimensional reduction (projection) object
 create_dim_reduction <- function(count_mat, key) {
   barcode_count <- dim(count_mat)[2]
diff --git a/tests/testthat/test-hdf5.R b/tests/testthat/test-hdf5.R
index 0c6ca29..4a782d0 100644
--- a/tests/testthat/test-hdf5.R
+++ b/tests/testthat/test-hdf5.R
@@ -51,6 +51,63 @@ test_that("can create hdf5", {
   expect(!is.null(hdf5r::readDataSet(louper_seurat_version)), "extra field is missing")
 })
 
+test_that("can create hdf5 with BPCells", {
+  skip_if_not_installed("BPCells")
+
+  barcode_count <- 5
+  proj <- create_dense_mat(barcode_count, 2)
+  count_mat <- create_count_mat_bpcells(100, barcode_count)
+  feature_ids <- paste0("Add_", rownames(count_mat))
+
+  clusters <- list("f1" = factor(c("a", "c", "b", "a", "b"), levels = c("a", "b", "c"), ordered = TRUE))
+  projections <- list("p1" = proj)
+  h5path <- sprintf("%s.h5", tempfile())
+
+  seurat_obj_version <- "1.2.3"
+  create_hdf5(count_mat, clusters, projections, h5path, feature_ids, seurat_obj_version)
+
+  count_mat <- as(count_mat, "dgCMatrix")
+  f <- hdf5r::h5file(h5path)
+
+  # spot check matrix
+  matrix_group <- hdf5r::openGroup(f, "matrix")
+  barcodes <- hdf5r::openLocation(matrix_group, "barcodes")
+  data <- hdf5r::openLocation(matrix_group, "data")
+  expect_equal(hdf5r::readDataSet(barcodes), paste0("col", 1:barcode_count))
+  expect_equal(hdf5r::readDataSet(data), count_mat@x)
+
+  features_group <- hdf5r::openGroup(matrix_group, "features")
+  feature_names <- hdf5r::openGroup(features_group, "name")
+  feature_ids_group <- hdf5r::openGroup(features_group, "id")
+  expect_equal(hdf5r::readDataSet(feature_names), rownames(count_mat))
+  expect_equal(hdf5r::readDataSet(feature_ids_group), feature_ids)
+
+  # spot check projections
+  projs_group <- hdf5r::openGroup(f, "projections")
+  proj_group <- hdf5r::openGroup(projs_group, "p1")
+  proj_dataset <- hdf5r::openLocation(proj_group, "data")
+  expect_equal(proj, hdf5r::readDataSet(proj_dataset))
+
+  # spot check clusters
+  clusters_group <- hdf5r::openGroup(f, "clusters")
+  cluster_group <- hdf5r::openGroup(clusters_group, "f1")
+  assignments <- hdf5r::openLocation(cluster_group, "assignments")
+  group_names <- hdf5r::openLocation(cluster_group, "group_names")
+  expect_equal(hdf5r::readDataSet(assignments), clusters[[1]]@.Data - 1)
+  expect_equal(hdf5r::readDataSet(group_names), levels(clusters[[1]]))
+
+  # spot check metadata
+  metadata <- hdf5r::openGroup(f, "metadata")
+
+  tool <- hdf5r::openLocation(metadata, "tool")
+  expect_equal(hdf5r::readDataSet(tool), "loupeR")
+
+  extra <- hdf5r::openGroup(metadata, "extra")
+  louper_seurat_version <- hdf5r::openLocation(extra, "loupeR_seurat_version")
+  val <- hdf5r::readDataSet(louper_seurat_version)
+  expect(!is.null(hdf5r::readDataSet(louper_seurat_version)), "extra field is missing")
+})
+
 test_that("can create hdf5 custom feature ids", {
   barcode_count <- 5
   count_mat <- create_count_mat(3, barcode_count)
diff --git a/tests/testthat/test-lib.R b/tests/testthat/test-lib.R
index db97b45..883aa04 100644
--- a/tests/testthat/test-lib.R
+++ b/tests/testthat/test-lib.R
@@ -59,6 +59,29 @@ test_that("can run create_loupe", {
   expect(x, "create_loupe returns TRUE")
 })
 
+test_that("can run create_loupe with BPCells", {
+  barcode_count <- 5
+  count_mat <- create_count_mat_bpcells(100, barcode_count, valid_barcodes = TRUE)
+  proj <- create_dense_mat(barcode_count, 2)
+  projections <- list("p1" = proj)
+
+  cluster <- factor(
+    c("a", "c", "b", "a", "b"),
+    levels = c("a", "b", "c"),
+    ordered = TRUE
+  )
+  clusters <- list("f1" = cluster)
+
+  x <- create_loupe(
+    count_mat,
+    clusters = clusters,
+    projections = projections,
+    executable_path = get_executable_path()
+  )
+
+  expect(x, "create_loupe returns TRUE")
+})
+
 test_that("can run create_loupe with integer projection matrix", {
   barcode_count <- 5
   count_mat <- create_count_mat(100, barcode_count, valid_barcodes = TRUE)