An understanding of cell-invasive behavior has been limited by the lack of in vivo models where this activity can be clearly visualized and manipulated. We show that a single cell in the Caenorhabditis elegans gonad, the anchor cell (AC), initiates uterine-vulval contact through a cell invasion event. Using genetic analysis, laser ablations, and cell-specific markers, we demonstrate that AC invasion is predominantly stimulated by the 1 degrees vulval lineage cells, which generate a diffusible signal that promotes AC invasive behavior toward these cells and further targets invasive processes between the two central 1 degrees vulval lineage cells. We also show that AC invasion is regulated by the AC response to this cue, as well as a vulval-independent mechanism that weakly drives invasion. These studies dissect the regulatory mechanisms that underlie a simple cell-invasive behavior in vivo, and introduce AC invasion as a model for understanding key checkpoints controlling cell invasion.