Twenty-two new species of poecilostome copepods associated with marine invertebrates are described from the West Indies, Madagascar, and Pacific coast of Panama. They are Anthessius nosybensis n. sp. and Discanthessius solitarius n. gen. n. sp. in the Anthessiidae; Cemihyclops tenuis n. sp., Hemicyclops tripartitus n. sp., H. humesi n. sp., H. magnus n. sp., and Leptinogaster minuta n. sp. in the Clausidiidae; Schedomolgus crenulatus n. sp. and S. parvipediger n. sp. in the Anchimolgidae; Kelleria multiovigera n. sp. in the Kelleridae; Lichomolgus angustus n. sp. and L. fusiformis n. sp. in the Lichomolgidae; Pseudanthessius acutus n. sp., P. asper n. sp., and Tubiporicola pediger n. gen. n. sp. in the Pseudanthessiidae; Acanthomolgus tenuispinatus n. sp. and Notoxynus lokobensis n. sp. in the Rhynchomolgidae; Eupolymniphilus occidentalis n. sp. and E. brevicaudatus n. sp. in the Sabellephilidae; Enalcyonium robustum n. sp. and E. grandisetigerum n. sp. in the Lamippidae; and O. binoviger n. sp. in the Myicolidae. Hemicyclops geminus Stock is synonymized with H. columnaris Humes which is now known as a species of amphi-American distribution. Hemicyclops columnaris Humes, Modiolicola trabalis Humes, and Ostrincola breviseti Ho and Kim are redescribed.