**Abstract** The reciprocal relations between sleep and affect have been a common focus in psychological research. Researchers studying affective processes often collect data multiple times a day over several days. Subjective sleep quality, on the other hand, is generally measured once at the beginning of the day. This difference in measurement frequency creates a challenge when analyzing these data, because standard dynamic models are not equipped for this. Furthermore, many of the popular approaches are based on the assumption of stationarity, meaning that processes are assumed to continue throughout the night in the same way as throughout the day. In this paper, we introduce a dynamic structural equation model that incorporates reciprocal relations between momentary affect and daily measures of sleep, tackling both of these challenges and also incorporating individual differences in these relations. To demonstrate the practical applicability of this model, we make use of an empirical example of positive and negative affect. Furthermore, we aim to give researchers the means to adapt or build on this model to align it with different research questions and other asynchronously measured variables.