ABSTRACT Animals experience seasonal fluctuations of photoperiod, food availability, temperature and precipitation. This affects their energy budget, often leading to seasonal reproduction. We review available literature and (re)‐analyse existing datasets on seasonal reproduction of South American caviomorph rodents that are characterised by long pregnancies, typically precocial young and short lactation. While births occur nearly year‐round in many species, reproductive investment and reproductive output (litter size, offspring mass and growth) vary seasonally, with largest litters often occurring in spring/summer. Male, as well as female, reproductive physiology varies across seasons in most of the investigated species. Experimental studies manipulating environmental aspects that usually change seasonally (photoperiod, nutrition, density) indicate a slightly different mechanistic basis driving seasonal reproduction in caviomorphs than in rodents of the Northern Hemisphere. Caviomorphs are a key component of various ecosystems and knowledge of their reproduction and how it might be influenced by climate change (i.e., mean and variance of temperature and rainfall) is urgently needed to predict future population trends.