diff --git a/Cargo.lock b/Cargo.lock
index a23798c69fe9753778879312f09715cec4447d17..c98ab05ef75ae57ae1d3250d2487dda23412c737 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -301,6 +301,27 @@ version = "0.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b41b7ea54a0c9d92199de89e20e58d49f02f8e699814ef3fdf266f6f748d15c7"
 
+[[package]]
+name = "binaryen"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a51ad23b3c7ab468d9daa948201921879ef0052e561c250fd0b326e6f000f2dd"
+dependencies = [
+ "binaryen-sys",
+]
+
+[[package]]
+name = "binaryen-sys"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df5829a7c89f7827e58866704e4dfdf48a635d73c6e5449c1a8a0ba5a319d28a"
+dependencies = [
+ "cc",
+ "cmake",
+ "heck",
+ "regex",
+]
+
 [[package]]
 name = "bitflags"
 version = "1.2.1"
@@ -477,6 +498,7 @@ dependencies = [
  "anyhow",
  "assert_matches",
  "async-std",
+ "binaryen",
  "blake2",
  "cargo-xbuild",
  "cargo_metadata 0.11.4",
diff --git a/Cargo.toml b/Cargo.toml
index 0c56fba7de99b50f9001bb4c4be66db61a6136b2..1252866ce5f28adeca8907f2687dadb231fdc94a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -41,6 +41,7 @@ serde = { version = "1.0.115", default-features = false, features = ["derive"] }
 serde_json = "1.0.57"
 tempfile = "3.1.0"
 url = { version = "2.1.1", features = ["serde"] }
+binaryen = "0.10.0"
 
 # dependencies for optional extrinsics feature
 async-std = { version = "1.6.2", optional = true }
diff --git a/README.md b/README.md
index e5c0f101ed89a8b13652ac7ad8a844a8b7e0984e..c3d97847ed0e747dfc12b1f686fa197ecc3864f5 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,8 @@ A CLI tool for helping setting up and managing WebAssembly smart contracts writt
 - **Prerequisites**
 
   - **rust-src**: `rustup component add rust-src`
-  - **wasm-opt**: https://github.com/WebAssembly/binaryen#tools
+  - A C++14 compiler is required for building the [binaryen](https://github.com/WebAssembly/binaryen)
+    dependency. `binaryen` is build automatically during the `cargo-contract` build process.
 
 - **Install latest version from [crates.io](https://crates.io/crates/cargo-contract)**
   - `cargo install cargo-contract`
diff --git a/src/cmd/build.rs b/src/cmd/build.rs
index 4fa2011b6abad37714227bed29cce0675383be28..9c8cfec2e7f42d081b14771254db03444fb6a94d 100644
--- a/src/cmd/build.rs
+++ b/src/cmd/build.rs
@@ -15,10 +15,9 @@
 // along with cargo-contract.  If not, see <http://www.gnu.org/licenses/>.
 
 use std::{
-    fs::metadata,
-    io::{self, Write},
+    fs::{metadata, File},
+    io::{Read, Write},
     path::PathBuf,
-    process::Command,
 };
 
 use crate::{
@@ -189,42 +188,34 @@ fn post_process_wasm(crate_metadata: &CrateMetadata) -> Result<()> {
     Ok(())
 }
 
-/// Attempts to perform optional wasm optimization using `wasm-opt`.
+/// Attempts to perform optional wasm optimization using `binaryen`.
 ///
 /// The intention is to reduce the size of bloated wasm binaries as a result of missing
 /// optimizations (or bugs?) between Rust and Wasm.
-///
-/// This step depends on the `wasm-opt` tool being installed. If it is not the build will still
-/// succeed, and the user will be encouraged to install it for further optimizations.
 fn optimize_wasm(crate_metadata: &CrateMetadata) -> Result<()> {
-    // check `wasm-opt` installed
-    if which::which("wasm-opt").is_err() {
-        println!(
-            "{}",
-            "wasm-opt is not installed. Install this tool on your system in order to \n\
-             reduce the size of your contract's Wasm binary. \n\
-             See https://github.com/WebAssembly/binaryen#tools"
-                .bright_yellow()
-        );
-        return Ok(());
-    }
-
     let mut optimized = crate_metadata.dest_wasm.clone();
     optimized.set_file_name(format!("{}-opt.wasm", crate_metadata.package_name));
 
-    let output = Command::new("wasm-opt")
-        .arg(crate_metadata.dest_wasm.as_os_str())
-        .arg("-O3") // execute -O3 optimization passes (spends potentially a lot of time optimizing)
-        .arg("-o")
-        .arg(optimized.as_os_str())
-        .output()?;
+    let codegen_config = binaryen::CodegenConfig {
+        // execute -O3 optimization passes (spends potentially a lot of time optimizing)
+        optimization_level: 3,
+        // the default
+        shrink_level: 1,
+        // the default
+        debug_info: false,
+    };
 
-    if !output.status.success() {
-        // Dump the output streams produced by wasm-opt into the stdout/stderr.
-        io::stdout().write_all(&output.stdout)?;
-        io::stderr().write_all(&output.stderr)?;
-        anyhow::bail!("wasm-opt optimization failed");
-    }
+    let mut dest_wasm_file = File::open(crate_metadata.dest_wasm.as_os_str())?;
+    let mut dest_wasm_file_content = Vec::new();
+    dest_wasm_file.read_to_end(&mut dest_wasm_file_content)?;
+
+    let mut module = binaryen::Module::read(&dest_wasm_file_content)
+        .map_err(|_| anyhow::anyhow!("binaryen failed to read file content"))?;
+    module.optimize(&codegen_config);
+    let optimized_wasm = module.write();
+
+    let mut optimized_wasm_file = File::create(optimized.as_os_str())?;
+    optimized_wasm_file.write_all(&optimized_wasm)?;
 
     let original_size = metadata(&crate_metadata.dest_wasm)?.len() as f64 / 1000.0;
     let optimized_size = metadata(&optimized)?.len() as f64 / 1000.0;