How long does this one act run? The question you're answering. donna@sancarloschildrenstheater.com June 26, 2018 Login to flag as inappropriate 2 Answer XXXX128351 July 13, 2018 authenticated Answer A one-act music usually lasts 90 minutes. ? Cindy Ripley June 27, 2018 vip Answer Hi Donna! In general, the one act shows run about 90 min. Have fun with this one - people are loving it!