Teaching introductory computer programming and choosing the proper tools and programming languages are challenging tasks. Most of the existing tools are not fully integrated into systems to support the teaching-learning processes. The present paper describes the usability evaluation of the Virtual Programming Lab module for Moodle (VPL-Moodle) based on a satisfaction questionnaire answered by 37 undergraduate students enrolled in CS1 and CS2 courses and 7 lecturers. Moreover, a heuristic evaluation performed by two specialists is also presented. Results of the descriptive and inferential analysis revealed mainly two things: a) the VPL-Moodle has a low level of usability in all five aspects analyzed by the students: satisfaction, efficiency, learnability, helpfulness, and environment control; and b) lecturers found some difficulties using the VPL-Moodle. A number of suggestions for the improvement of the VPL-Moodle interface are provided based on the findings of the paper.