Background: Temporomandibular joint is one of the complex joints in the human body. The integrity of the joint is dependent on the unique structure and balance of ligaments and muscles. TM joint dysfunction is described in terms of myofascial pain, internal derangement and cervical spine dysfunction. The association between postural deviations due to smartphone addictions and TMJ dysfunction is overlooked. The overwhelming use of smartphones has become the need of the hour for young adults in COVID-19 lockdown. During this exceptional situation, a smartphone is the most handy device for entertainment, educational purpose and social connect. Therefore, this study was conducted to see the Influence of smartphone addiction on Tempero-mandibular joint function during Covid 19 lockdown among urban young adults. Materials and Methods: This was a multidisciplinary web-based study. Outcome measures used were SmartPhone Addiction Scale Short Version (SAS-SV) and Jaw functional limitation Scale 20 (JFLS-20) among young adults. Results: Out of 314 participants, SAS-SA score was > 33 in 88 (61.97%) females and >31 in 106 (61.63%) males. The Scores of subscales of JFLS-20 in this study are as follows: In females, for mastication (mean + SD) was (2.8 + 2.2), for mobility was (2.4+2.3), and for verbal and non-verbal communication was (2.5 + 2.4). In males, for mastication (mean + SD) was (2.6 + 2.3), for mobility was (2.6+2.3), and for verbal and non-verbal communication was (2.6 + 2.2). Conclusion: Impact of smartphone addiction can be seen in the upper quarter. This further affects TM joint function including mastication, mobility and verbal and non- verbal communication.