•Agile and non-agile software development typically have similar front-end phases.•Agile software development with less detail in the front-end phase performed better.•The front-end phase content should be context-dependent avoiding one-size-fits-all.•Studies show a lack of robustness regarding causal connections.•There has been a low research interest in the front-end phase. Software development of new products and services often involves a front-end phase where user needs are analysed, costs and benefits are estimated, and initial plans are created. This study aims to learn more about how the introduction of agile software development has affected practices and outcomes related to cost and benefit estimation in this front-end phase and to understand better what would improve this phase. We identified, reviewed and aggregated the results from 42 relevant research articles by searching literature databases and snowballing relevant articles. The front-end phase of agile was found to be, on average, similar and just as comprehensive as that of non-agile software development. This may be unfortunate, given the finding that more successful agile software development is connected with less detail in cost estimation and planning-related activities. A less comprehensive front-end phase may be especially beneficial for low-risk agile software development. The results of this review suggest that agile principles, so far, have had a limited influence on the front-end phase. We recommend more flexibility and context-dependency in how the front-end phase of agile software development is conducted, including less comprehensive estimation and planning activities for low-risk software development contexts.