Harris then again took over as caretaker boss on 10 March 2015, when Holloway was sacked. By the time Harris took over, Millwall were already virtually, whilst not mathematically, relegated, however Harris went on to win 2 and draw 4 of his 9 games in charge, almost keeping the Lions in the Championship. On 28 April, the Lions were officially relegated to League One following Rotherham United's 2–1 win against Reading, however, Harris was confirmed as Millwall's permanent manager less than 24 hours later, with his assistant being his 2004 FA Cup Final teammate, David Livermore.