Objective: This study is aimed to explore severe mental illness (SMI), mental well-being (MWB), and Mediterranean Diet adherence (MedDiet) among university students. Participants: University students in Northern Italy (sample size = 502) Methods: Cross-sectional survey was conducted in 2019. The questionnaires included Warwick-Edinburgh Mental Well-Being Scale for MWB, K6 for SMI, Mediterranean Diet Adherence Screener for MedDiet. Multivariable regressions were mainly performed (p < 0.05 as significant). Results: MWB was high in 3.93% of the participants and low in 23.97%. SMI was probable in 21.87%. MedDiet adherence was high in 2.19% and low in 35.06%. Mainly, poor/very poor perceived health, Economics/Legal/Strategic Sciences courses, and not being on time with exams showed associations with both lower MWB and probable SMI. Gender and some lifestyle, dietary, and university factors predicted MedDiet. MWB and MedDiet were positively associated. Conclusions: This study found high levels of mental issues and low MedDiet. Modifiable factors at university level should be investigated to design preventive interventions.