diff --git a/lib/nmatrix/shortcuts.rb b/lib/nmatrix/shortcuts.rb
index 9c384df7..9af205c7 100644
--- a/lib/nmatrix/shortcuts.rb
+++ b/lib/nmatrix/shortcuts.rb
@@ -282,35 +282,45 @@ def diagonal(entries, opts={})
     #                  can receive any number of arguments. Optionally, the last entry of +params+ is 
     #                  a hash of options from NMatrix#initialize. All other entries of +params+ are 
     #                  the blocks of the desired block-diagonal matrix, which are supplied
-    #                  as square 2D NMatrix objects.
+    #                  as square 2D NMatrix objects, or alternatively as arrays of arrays 
+    #                  (with dimensions corresponding to square matrices).
     # * *Returns*
     #   - NMatrix of block-diagonal form filled with specified matrices
     #     as the blocks along the diagonal.
     #
     # * *Example* 
     #
-    #  a = NMatrix.new([2,2],[1,2,3,4])
-    #  b = NMatrix.new([1,1],[123],dtype: :int32)
-    #  c = NMatrix.new([3,3],[1,2,3,1,2,3,1,2,3], dtype: :float64)
-    #  m = NMatrix.block_diagonal(a,b,c,dtype: :int64, stype: :yale)
+    #  a = NMatrix.new([2,2], [1,2,3,4])
+    #  b = NMatrix.new([1,1], [123], dtype: :float64)
+    #  c = Array.new(2) { [[10,10], [10,10]] }
+    #  d = Array[[1,2,3], [4,5,6], [7,8,9]]
+    #  m = NMatrix.block_diagonal(a, b, *c, d, dtype: :int64, stype: :yale)
     #      => 
     #      [
-    #        [1, 2,   0, 0, 0, 0]
-    #        [3, 4,   0, 0, 0, 0]
-    #        [0, 0, 123, 0, 0, 0]
-    #        [0, 0,   0, 1, 2, 3]
-    #        [0, 0,   0, 1, 2, 3]
-    #        [0, 0,   0, 1, 2, 3]
+    #        [1, 2,   0,  0,  0,  0,  0, 0, 0, 0]
+    #        [3, 4,   0,  0,  0,  0,  0, 0, 0, 0]
+    #        [0, 0, 123,  0,  0,  0,  0, 0, 0, 0]
+    #        [0, 0,   0, 10, 10,  0,  0, 0, 0, 0]
+    #        [0, 0,   0, 10, 10,  0,  0, 0, 0, 0]
+    #        [0, 0,   0,  0,  0, 10, 10, 0, 0, 0]
+    #        [0, 0,   0,  0,  0, 10, 10, 0, 0, 0]
+    #        [0, 0,   0,  0,  0,  0,  0, 1, 2, 3]
+    #        [0, 0,   0,  0,  0,  0,  0, 4, 5, 6]
+    #        [0, 0,   0,  0,  0,  0,  0, 7, 8, 9]
     #      ]
-    #
+    #          
     def block_diagonal(*params)
       options = params.last.is_a?(Hash) ? params.pop : {}
 
+      params.each_index do |i|
+        params[i] = params[i].to_nm if params[i].is_a?(Array) # Convert Array to NMatrix
+      end
+
       block_sizes = [] #holds the size of each matrix block
       params.each do |b|
-        raise ArgumentError, "Only NMatrix objects allowed" unless b.is_a?(NMatrix)
-        raise ArgumentError, "Only 2D matrices allowed" unless b.shape.size == 2
-        raise ArgumentError, "Only square matrices allowed" unless b.shape[0] == b.shape[1]
+        raise ArgumentError, "Only NMatrix or Array objects allowed" unless b.is_a?(NMatrix)
+        raise ArgumentError, "Only 2D matrices or 2D arrays allowed" unless b.shape.size == 2
+        raise ArgumentError, "Only square-shaped blocks allowed" unless b.shape[0] == b.shape[1]
         block_sizes << b.shape[0]
       end
 
diff --git a/spec/shortcuts_spec.rb b/spec/shortcuts_spec.rb
index 677864fc..07f187a3 100644
--- a/spec/shortcuts_spec.rb
+++ b/spec/shortcuts_spec.rb
@@ -69,19 +69,23 @@
     [:dense, :yale, :list].each do |stype|
       context "#block_diagonal #{dtype} #{stype}" do
         it "block_diagonal() creates a block-diagonal NMatrix" do
-          a = NMatrix.new([2,2],[1,2,
-                                 3,4])
-          b = NMatrix.new([1,1],[123.0])
-          c = NMatrix.new([3,3],[1,2,3,
-                                 1,2,3,
-                                 1,2,3])
-          m = NMatrix.block_diagonal(a,b,c, dtype: dtype, stype: stype)
-          expect(m).to eq(NMatrix.new([6,6], [1, 2,   0, 0, 0, 0,
-                                              3, 4,   0, 0, 0, 0,
-                                              0, 0, 123, 0, 0, 0,
-                                              0, 0,   0, 1, 2, 3,
-                                              0, 0,   0, 1, 2, 3,
-                                              0, 0,   0, 1, 2, 3], dtype: dtype, stype: stype))
+          a = NMatrix.new([2,2], [1,2,
+                                  3,4])
+          b = NMatrix.new([1,1], [123.0])
+          c = NMatrix.new([3,3], [1,2,3,
+                                  1,2,3,
+                                  1,2,3])
+          d = Array[ [1,1,1], [2,2,2], [3,3,3] ] 
+          m = NMatrix.block_diagonal(a, b, c, d, dtype: dtype, stype: stype)
+          expect(m).to eq(NMatrix.new([9,9], [1, 2,   0, 0, 0, 0, 0, 0, 0,
+                                              3, 4,   0, 0, 0, 0, 0, 0, 0,
+                                              0, 0, 123, 0, 0, 0, 0, 0, 0,
+                                              0, 0,   0, 1, 2, 3, 0, 0, 0,
+                                              0, 0,   0, 1, 2, 3, 0, 0, 0,
+                                              0, 0,   0, 1, 2, 3, 0, 0, 0,
+                                              0, 0,   0, 0, 0, 0, 1, 1, 1,
+                                              0, 0,   0, 0, 0, 0, 2, 2, 2,
+                                              0, 0,   0, 0, 0, 0, 3, 3, 3], dtype: dtype, stype: stype))
         end
       end
     end