As crowdsourcing gains popularity, organizations seek ways to systematically and reliably engage with their own skilled and trusted workforce, to enrich their data creation. In this setting, mobile crowdsourcing platforms allow for opportunistic task executions and thus, potentially, for higher execution throughput. How to engage (and retain) employees in enterprise crowdsourcing campaigns is, however, an open research topic. When would employees be more willing to contribute in a campaign? What would be the right moment to seek for their contribution? This thesis contributes to knowledge on those matters. To answer these questions, we surveyed 93 IBM employees, to discover the factors that might affect engagement in enterprise mobile crowdsourcing. The survey informed the design of an experiment that involved 83 employees of a multinational company. The experiment aimed at studying the effectiveness of different notification strategies aimed at nudging employees for task execution during their work time. We studied how factors such as time and context of notification can affect the participation and retention of employees in crowdsourcing campaigns. Results show that break times are the best to solicit help from employees. In addition, we discovered that “aggressive” notification strategies act as deterrent for participation, and that moderate yet regular nudges are the most likely to yield useful contributions.