Skacel joined Dundee United on 26 October 2012 contracted until 30 January 2013. He instantly caused controversy by, as he had previously hinted on his Twitter account, selecting the number 51 shirt at his new club in reference to Hearts' victory over rivals Hibernian in the Scottish Cup Final. Manager Peter Houston apologised to Hibs fans saying he was unaware of the significance of the number and would not have allowed Skácel to wear 51 had he known his reasons for selecting it. Skácel made his debut a day after signing, as a second-half substitute in a 1–0 victory over St Mirren at St Mirren Park. He faced his former club, Hearts, four days later on 31 October in a Scottish League Cup quarter-final at Tannadice and received a warm reception from the travelling Hearts support when he appeared as a substitute in extra time as United were eventually defeated 5–4 on penalties. His first seven appearances for Dundee United were as a substitute, before making his first start on 27 November 2012 in a 2–1 home defeat to Motherwell in the league. This match also marked his 100th appearance in the Scottish Premier League. He scored his first goal for the "Terrors" on 15 December 2012, in a thrilling 4–4 league draw with Inverness Caledonian Thistle at Tannadice. He made a total of 16 appearances for United, scoring once as he was utilized primarily as a second-half substitute with ten of his appearances coming from the bench.