Alcohol dependence is a common disorder with a continuum regarding severity. Most alcohol-dependent persons have a moderate level of dependence and live under socially orderly conditions. Treatment-seeking in this group is low, mainly due to stigma and because treatment options are seen as unappealing. Alcohol is a relevant topic to discuss in many primary care (PC) consultations and PC is less stigmatizing to visit compared to addiction care units for people with alcohol problems. However, general practitioners (GPs) hesitate to engage in treating alcohol problems due to time constraints and lack of knowledge. Screening and brief interventions are effective for high consumers but there are few studies on dependence. This is a two-group, parallel, randomized controlled trial (RCT). The aim is to study whether an Internet-based Cognitive Behavioral Treatment (iCBT) when added to treatment as usual (TAU) is more effective than TAU only for alcohol dependence in PC. Two hundred and sixty adults with alcohol dependence will be included. Participants are randomized to iCBT and TAU or TAU only. The primary study outcome is alcohol consumption in grams per week and heavy-drinking days. Secondary outcomes include alcohol-related problem severity, number of diagnostic criteria for alcohol dependence, depression and anxiety symptoms, health-related quality of life and biochemical markers for high consumption and liver pathology. Data will be analyzed using mixed-effect models. Internet-based interventions are attractive to, and have been shown to reach, people with alcohol problems. Yet there are no studies investigating the efficacy of Internet treatment of alcohol dependence in PC. In this study we hypothesize that iCBT when added to TAU will improve treatment outcome for alcohol dependence in PC, compared to TAU only. If effective, iCBT can be distributed to the public to a low cost for a stakeholder and has the opportunity to reduce both short-term and long-term public health costs. ISRCTN69957414. Retrospectively registered on 7 June 2018.