Objectives: Text neck syndrome was first described by Fishman D. It refers to neck pain caused by repetitive stress injury resulting from prolonged neck flexion among smartphone users. The association of neck disability with various behaviors during the use of smartphones is still unclear in the literature. Therefore, we aimed to estimate the frequency of such factors and evaluate whether they contribute to text neck. Methods: A cross-sectional study was conducted at six medical colleges in Jeddah, Saudi Arabia, from July 2020 to January 2021. An electronic, self-administered questionnaire was distributed to medical students online. In addition, participants were asked to complete the smartphone addiction scale-short version (SAS-SV) and the neck disability index (NDI). Results: A total of 428 medical students participated, of which 304 (71.02%) were female, while 124 (28.97%) were male. The mean age was 22.11 ± 2.07 years. The prevalence of text neck syndrome was 68.1%. Among the participants, 49.5% had mild, 16.1% had moderate, and 2.6% had severe neck disabilities. The Spearman correlation coefficient showed a moderate positive correlation between SAS-SV and the NDI (rs = 0.328, P < 0.001). Conclusion: The current study found that most medical students had a neck disability, and there was a significant association between text neck syndrome and smartphone use. In addition, a lack of appropriate neck positioning and prolonged use of smartphones were found in most students. Therefore, more emphasis should be placed on raising awareness of the necessity of maintaining appropriate sitting posture and limiting the duration of mobile phone use.