diff --git a/src/script/sign.h b/src/script/sign.h
--- a/src/script/sign.h
+++ b/src/script/sign.h
@@ -617,6 +617,12 @@
                    CMutableTransaction &txTo, unsigned int nIn,
                    SigHashType sigHashType);
 
+/** Signs a PSBTInput */
+bool SignPSBTInput(const SigningProvider &provider,
+                   const CMutableTransaction &tx, PSBTInput &input,
+                   SignatureData &sigdata, int index,
+                   SigHashType sighash = SigHashType());
+
 /** Extract signature data from a transaction input, and insert it. */
 SignatureData DataFromTransaction(const CMutableTransaction &tx,
                                   unsigned int nIn, const CTxOut &txout);
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -217,6 +217,32 @@
     return sigdata.complete;
 }
 
+bool SignPSBTInput(const SigningProvider &provider,
+                   const CMutableTransaction &tx, PSBTInput &input,
+                   SignatureData &sigdata, int index, SigHashType sighash) {
+    // if this input has a final scriptsig, don't do anything with it
+    if (!input.final_script_sig.empty()) {
+        return true;
+    }
+
+    // Fill SignatureData with input info
+    input.FillSignatureData(sigdata);
+
+    // Get UTXO
+    CTxOut utxo;
+    if (input.utxo.IsNull()) {
+        return false;
+    }
+
+    utxo = input.utxo;
+    MutableTransactionSignatureCreator creator(&tx, index, utxo.nValue,
+                                               sighash);
+    bool sig_complete =
+        ProduceSignature(provider, creator, utxo.scriptPubKey, sigdata);
+    input.FromSignatureData(sigdata);
+    return sig_complete;
+}
+
 class SignatureExtractorChecker final : public BaseSignatureChecker {
 private:
     SignatureData &sigdata;