diff --git a/r/NAMESPACE b/r/NAMESPACE
index ef32160a6..c76f380ec 100644
--- a/r/NAMESPACE
+++ b/r/NAMESPACE
@@ -65,7 +65,6 @@ S3method(c,nanoarrow_vctr)
 S3method(convert_array,default)
 S3method(convert_array,double)
 S3method(convert_array,factor)
-S3method(convert_array,matrix)
 S3method(convert_array,nanoarrow_vctr)
 S3method(convert_array,vctrs_partial_frame)
 S3method(convert_array_extension,default)
diff --git a/r/R/convert-array.R b/r/R/convert-array.R
index 41d90e3aa..a33273e70 100644
--- a/r/R/convert-array.R
+++ b/r/R/convert-array.R
@@ -173,37 +173,6 @@ convert_array.double <- function(array, to, ...) {
   }
 }
 
-#' @export
-convert_array.matrix <- function(array, to, ...) {
-  schema <- infer_nanoarrow_schema(array)
-  parsed <- nanoarrow_schema_parse(schema)
-  if (parsed$type != "fixed_size_list") {
-    stop_cant_convert_array(array, to)
-  }
-
-  if (identical(to, matrix())) {
-    to <- matrix(
-      infer_nanoarrow_ptype(array$children[[1]]),
-      nrow = 0,
-      ncol = parsed$fixed_size
-    )
-  }
-
-  if (ncol(to) != parsed$fixed_size) {
-    stop(
-      sprintf(
-        "Can't convert fixed_size_list(list_size=%d) to matrix with %d cols",
-        parsed$fixed_size,
-        ncol(to)
-      )
-    )
-  }
-
-  attributes(to) <- NULL
-  child_vctr <- convert_array(array$children[[1]], to)
-  matrix(child_vctr, ncol = parsed$fixed_size, byrow = TRUE)
-}
-
 #' @export
 convert_array.vctrs_partial_frame <- function(array, to, ...) {
   ptype <- infer_nanoarrow_ptype(array)
diff --git a/r/src/materialize.c b/r/src/materialize.c
index 94cd9a31b..0ece9c3f3 100644
--- a/r/src/materialize.c
+++ b/r/src/materialize.c
@@ -622,6 +622,12 @@ static int nanoarrow_materialize_matrix(struct RConverter* converter,
       return EINVAL;
   }
 
+  if (converter->schema_view.fixed_size != Rf_ncols(converter->ptype_view.ptype)) {
+    Rf_error("Can't convert fixed_size_list(list_size=%d) to matrix with %d cols",
+             (int)converter->schema_view.fixed_size,
+             Rf_ncols(converter->ptype_view.ptype));
+  }
+
   int64_t raw_src_offset = src->array_view->array->offset + src->offset;
   int64_t list_length = src->array_view->layout.child_size_elements;
   int64_t offset;
diff --git a/r/tests/testthat/test-convert-array.R b/r/tests/testthat/test-convert-array.R
index ea39f4df7..e6a18f850 100644
--- a/r/tests/testthat/test-convert-array.R
+++ b/r/tests/testthat/test-convert-array.R
@@ -1045,7 +1045,6 @@ test_that("convert to vector works for fixed_size_list_of() -> matrix()", {
   mat <- matrix(1:6, ncol = 2, byrow = TRUE)
   array <- as_nanoarrow_array(mat)
 
-  expect_identical(convert_array(array, matrix()), mat)
   expect_identical(
     convert_array(array, matrix(double(), ncol = 2)),
     matrix(as.double(1:6), ncol = 2, byrow = TRUE)