CrowdSearch is a system that uses human workers on Amazon Mechanical Turk to validate image search results in real-time on mobile phones. It has three main components: 1) an image search engine that extracts features from query images and searches a database, 2) a crowdsearch algorithm that optimizes delay and cost by predicting validation times and results, and 3) a system implementation that coordinates the image search engine and human validators. The system was able to improve search precision using human validation while meeting user-specified deadlines in experimental evaluations.