Dataset comprising data on the lifetime reproductive success (LRS) of 879 individually marked long-tailed tits Aegithalos caudatus, a cooperatively breeding passerine. LRS is measured in terms of the number of local recruits into the breeding population in the study area, controlling for fledgling sex and extra-pair paternity. LRS data are then partitioned into direct and indirect fitness components, quantified as genetic equivalents. Partitioning of fitness follows Hamilton’s definition of inclusive fitness: (a) direct fitness is measured as the production of offspring, stripped of the social effect of helpers on productivity; (b) indirect fitness is calculated from the mean marginal effect of a helper on productivity, adjusted for helper relatedness. Inclusive fitness is calculated by summing direct and indirect fitness. Full details about this dataset can be found at https://doi.org/10.5285/0e55f507-e5bd-4678-a5ea-8c3ffb62d3ac
