One of the common assumptions in the study of the evolution of parental care is that trade-offs exist between parental investment and other fitness-related traits. In general, this body of work follows the traditional definition that parental investment (in the current offspring) decreases that individual’s ability to invest in future reproduction (Trivers 1972). However, examination of the empirical evidence shows that assuming a trade-off between parental and mating effort is not always appropriate. This overemphasis on a trade-off between mating and parental effort has arisen in part because of an oversimplification of female reproductive strategies, a failure to consider interactions between the sexes, and a tendency to consider behaviours as unifunctional, thereby ignoring the more complex relationship between mating and parental effort in many species. Here, we first examine the empirical evidence for trade-offs between mating and parental effort in males and females to ask when trade-offs occur and what pattern they take. By highlighting a number of exemplar species, we then explore how the presence or absence of trade-offs relates to mate choice and sexual selection in both sexes. Finally, we highlight the importance of considering individual variation, which has been particularly overlooked in examinations of female investment, and how preferences in one sex may influence the existence and our interpretation of apparent trade-offs in the other sex.