diff --git a/3.12.0/Dockerfile b/3.12.0/Dockerfile
new file mode 100644
index 0000000..8354cd4
--- /dev/null
+++ b/3.12.0/Dockerfile
@@ -0,0 +1,19 @@
+FROM debian:wheezy
+
+MAINTAINER Jo Shields <jo.shields@xamarin.com>
+
+#based on dockerfile by Michael Friis <friism@gmail.com>
+
+RUN apt-get update \
+	&& apt-get install -y curl
+	&& rm -rf /var/lib/apt/lists/*
+
+RUN apt-key adv --keyserver pgp.mit.edu --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
+
+RUN echo "deb http://download.mono-project.com/repo/debian wheezy/snapshots/3.12.0 main" > /etc/apt/sources.list.d/mono-xamarin.list \
+	&& apt-get update \
+	&& apt-get install -y mono-devel fsharp mono-vbnc nuget \
+	&& rm -rf /var/lib/apt/lists/*
+
+RUN mozroots --machine --import --sync --quiet
+
diff --git a/3.12.0/onbuild/Dockerfile b/3.12.0/onbuild/Dockerfile
new file mode 100644
index 0000000..94da5e4
--- /dev/null
+++ b/3.12.0/onbuild/Dockerfile
@@ -0,0 +1,12 @@
+FROM mono:3.12.0
+
+MAINTAINER Jo Shields <jo.shields@xamarin.com>
+
+RUN mkdir -p /usr/src/app/{source,build}
+WORKDIR /usr/src/app/source
+
+ONBUILD ADD . /usr/src/app/source
+ONBUILD RUN nuget restore -NonInteractive
+ONBUILD RUN xbuild /property:Configuration=Release /property:OutDir=/usr/src/app/build/
+ONBUILD RUN rm -rf /usr/src/app/source
+ONBUILD WORKDIR /usr/src/app/build
diff --git a/README.md b/README.md
index 0ef21e3..abeb04c 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,9 @@
 # Supported tags and `Dockerfile` links
 
-- [`latest` (*Dockerfile*)](https://github.com/mono/docker/blob/master/3.10.0/Dockerfile)
-- [`onbuild` (*onbuild/Dockerfile*)](https://github.com/mono/docker/blob/master/3.10.0/onbuild/Dockerfile)
+- [`latest` (*Dockerfile*)](https://github.com/mono/docker/blob/master/3.12.0/Dockerfile)
+- [`onbuild` (*onbuild/Dockerfile*)](https://github.com/mono/docker/blob/master/3.12.0/onbuild/Dockerfile)
+- [`3.12.0` (*Dockerfile*)](https://github.com/mono/docker/blob/master/3.12.0/Dockerfile)
+- [`3.12.0-onbuild` (*onbuild/Dockerfile*)](https://github.com/mono/docker/blob/master/3.12.0/onbuild/Dockerfile)
 - [`3.10.0` (*Dockerfile*)](https://github.com/mono/docker/blob/master/3.10.0/Dockerfile)
 - [`3.10.0-onbuild` (*onbuild/Dockerfile*)](https://github.com/mono/docker/blob/master/3.10.0/onbuild/Dockerfile)
 - [`3.8.0` (*Dockerfile*)](https://github.com/mono/docker/blob/master/3.8.0/Dockerfile)