In this work, we aim to evaluate the impact of internships on recent graduates entering the workforce for four UCSC School of Engineering programs. Civil Engineering and Geological Engineering students take a 400-hour internship, generally during the summer months preceding their senior year. Computer Science and Industrial Engineering students optionally take a semester-long senior-year internship. These professional internships are integrated learning experiences in an organization (CDIO standard 7) which foster student disciplinary knowledge (CDIO 1), analytic reasoning and problem solving (CDIO 2.1), perseverance and flexibility (CDIO 2.4.2), critical thinking (CDIO 2.4.4), teamwork (CDIO 3.1), communication skills (CDIO 3.2), and conceiving, designing, implementing and operating systems in a real context (CDIO 4). This study considers data gathered through an online perception survey applied to all those program graduates that signed up for an internship from 2016 onwards, and have graduated at least a semester ago. It also shows that graduates from all programs state that the internships strengthened their technical knowledge, personal and interpersonal skills. Regarding product, process, and system building skills, these numbers increase to over 90%, except for their ability to operate them (CDIO 4.6), which is closer to 75% for Civil and Geological Engineering. Our results also show that about 70% of graduates who did a semester-long internship feel the internship helped them find a job within six months of graduating, whereas less than a third of students doing the shorter internship felt so. Around 40% of graduates entered into a contractual relationship with their internship company, except for graduates of the Industrial Engineering program, where this number doubles. Students were also asked to identify those strengths and weaknesses that helped and hindered them during their internship. Among their strengths, they identified their teamwork and leadership skills, and among their weaknesses, they identified their lack of self-confidence and experience.