In recent years a bewildering array of smartphone applications (“apps”) has emerged to support separated parents' communication. Post-separation parenting apps vary in cost and features; they typically comprise a messaging tool, shared calendar, expense tracker and a means to export records for legal purposes. A key challenge for separated parents and family law practitioners alike is knowing which apps or app feature(s) can work well for different family contexts, needs and budgets. The present study sought to evaluate nine popular post-separation parenting apps and their features using small-n Human–Computer Interaction methods. Mediators role-played high conflict ex-couples while completing a set of five common post-separation communication or organizational tasks. A cross-case analysis of ratings was conducted. We found that (a) many of the mediators changed their apparent enthusiasm for co-parenting apps once they had used the apps themselves; (b) all nine apps were rated somewhere between “Poor” to Fair’; and (c) features of some of the best-known apps were not rated as highly as some of the features of more recent, lesser-known apps.