The CMS experiment implements a sophisticated two-level triggering system composed of Level- 1 (L1), instrumented by custom-design hardware boards, and a software High Level Trigger. A new Level-1 trigger architecture with improved performance is now being used to maintain high physics efficiency for the more challenging luminosity conditions experienced during Run II. The CMS muon detector contains complementary and partially redundant muon detection systems: the Cathode Strip Chambers (CSC), Drift Tubes (DT) and Resistive Plate Chambers (RPC). The upgraded L1 muon trigger combines information from these three detectors to reconstruct muons and obtain a better efficiency and lower rates. Algorithms for the selection of events with muons, both for precision measurements and searches for new physics beyond the Standard Model, are described in detail. The performance of the upgraded muon trigger system will be presented, based on proton-proton collision data collected in 2017.