The present trial examined the effectiveness of brief interventions for smokers who joined the Hong Kong Quit to Win Contest to quit smoking. A block randomized controlled trial allocated 1003 adult daily smokers to three groups: (i) The TEL group (n = 338) received a 5-min nurse-led telephone counselling; (ii) The SMS group (n = 335) received eight text messages through mobile phone and (iii) The CONTROL group (n = 330) did not receive the above interventions. Participants with biochemically verified abstinence at 6-month follow-up could receive cash incentive. The primary outcome was the self-reported 7-day point prevalence (PP) of tobacco abstinence at 6-month follow-up. The abstinence rate in the TEL, SMS and CONTROL group was 22.2, 20.6 and 20.3%, respectively (P for TEL versus CONTROL = 0.32; P for SMS versus CONTROL = 0.40). When abstinence at 2-, 6- and 12-month follow-up was modelled simultaneously, the TEL group had a higher abstinence than the CONTROL group (Adjusted OR = 1.38, 95% CI = 1.01--1.88, P = 0.04). In the Quit to Win Contest, the brief telephone counselling might have increased abstinence, but the text messages had no significant effect. Further studies on intensive intervention and interactive messaging services are warranted.