diff --git a/pkgs/build-support/ocaml/oasis.nix b/pkgs/build-support/ocaml/oasis.nix
new file mode 100644
index 00000000000..74977486f2f
--- /dev/null
+++ b/pkgs/build-support/ocaml/oasis.nix
@@ -0,0 +1,46 @@
+{ stdenv, ocaml_oasis, ocaml, findlib, ocamlbuild }:
+
+{ pname, version, buildInputs ? [], meta ? { platforms = ocaml.meta.platforms or []; },
+  minimumOCamlVersion ? null,
+  createFindlibDestdir ? true,
+  dontStrip ? true,
+  ...
+}@args:
+
+if args ? minimumOCamlVersion &&
+   ! stdenv.lib.versionAtLeast ocaml.version args.minimumOCamlVersion
+then throw "${pname}-${version} is not available for OCaml ${ocaml.version}"
+else
+
+stdenv.mkDerivation (args // {
+  name = "ocaml${ocaml.version}-${pname}-${version}";
+
+  buildInputs = [ ocaml findlib ocamlbuild ocaml_oasis ] ++ buildInputs;
+
+  inherit createFindlibDestdir;
+  inherit dontStrip;
+
+  buildPhase = ''
+    runHook preBuild
+    oasis setup
+    ocaml setup.ml -configure
+    ocaml setup.ml -build
+    runHook postBuild
+  '';
+
+  checkPhase = ''
+    runHook preCheck
+    ocaml setup.ml -test
+    runHook postCheck
+  '';
+
+  installPhase = ''
+    runHook preInstall
+    mkdir -p $out
+    sed -i s+/usr/local+$out+g setup.ml
+    sed -i s+/usr/local+$out+g setup.data
+    prefix=$OCAMLFIND_DESTDIR ocaml setup.ml -install
+    runHook postInstall
+  '';
+
+})
diff --git a/pkgs/development/ocaml-modules/tcslib/default.nix b/pkgs/development/ocaml-modules/tcslib/default.nix
new file mode 100644
index 00000000000..9d1d5a8096c
--- /dev/null
+++ b/pkgs/development/ocaml-modules/tcslib/default.nix
@@ -0,0 +1,25 @@
+{ lib, fetchFromGitHub, ocamlPackages, buildOasisPackage, ounit, ocaml_extlib, num }:
+
+buildOasisPackage rec {
+  pname = "tcslib";
+  version = "0.3";
+
+  minimumOCamlVersion = "4.03.0";
+
+  src = fetchFromGitHub {
+    owner  = "tcsprojects";
+    repo   = "tcslib";
+    rev    = "v${version}";
+    sha256 = "05g6m82blsccq8wx8knxv6a5fzww7hi624jx91f9h87nk2fsplhi";
+  };
+
+  buildInputs = [ ounit ];
+  propagatedBuildInputs = [ ocaml_extlib num ];
+
+  meta = {
+    homepage = https://github.com/tcsprojects/tcslib;
+    description = "A multi-purpose library for OCaml";
+    license = lib.licenses.bsd3;
+    maintainers = with lib.maintainers; [ mgttlinger ];
+  };
+}
diff --git a/pkgs/top-level/ocaml-packages.nix b/pkgs/top-level/ocaml-packages.nix
index 1df001895b7..5249f848d01 100644
--- a/pkgs/top-level/ocaml-packages.nix
+++ b/pkgs/top-level/ocaml-packages.nix
@@ -12,6 +12,8 @@ let
 
     buildOcaml = callPackage ../build-support/ocaml { };
 
+    buildOasisPackage = callPackage ../build-support/ocaml/oasis.nix { };
+
     buildDunePackage = callPackage ../build-support/ocaml/dune.nix {};
 
     alcotest = callPackage ../development/ocaml-modules/alcotest {};
@@ -725,6 +727,8 @@ let
 
     stringext = callPackage ../development/ocaml-modules/stringext { };
 
+    tcslib = callPackage ../development/ocaml-modules/tcslib { };
+
     toml = callPackage ../development/ocaml-modules/toml { };
 
     topkg = callPackage ../development/ocaml-modules/topkg { };