In the Internet era, the communication environment of university students’ ideological and mental health education (IMHE) has become more complex. Few studies have focused on the communication effect of Internet contact on the IMHE of university students. This study adopts a questionnaire survey method to explore Internet contact and IMHE of 2294 university students. The study found that Internet was the most important information source for university students. Nearly half of the university students spent 2–5 hours online per day for entertainment or fragmented learning. Educational films, communication and discussion, and classroom teaching were the three most popular forms of IMHE for university students, while comments on current events, psychological counseling, and national policies and regulations were the three favorite contents. Internet contact during (ICD) had significant impacts on the cognitive and behavioral communication effect of IMHE among Chinese university students. The emotional dimension had the best communication effect, followed by behavior and will, and finally the cognitive dimension. After conducting IMHE, university students had stronger emotional management abilities and were more optimistic. This finding suggested that when developing and implementing IMHE intervention for university students in schools, special attention should be paid to the impact of ICD differences on the communication effect of IMHE, especially cognitive communication needed improvement.