Intubated patients are at risk of oral health problems. Although a variety of oral care regimens for intubated patients have been studied, there is a lack of research on the effects of combination oral care that includes tooth brushing, chlorhexidine and cold water. This open-labelled, randomized, controlled trial aimed to evaluate the effects of combination oral care on oral health status. Participants aged 20 years and older were recruited on the first day after intubation through convenience sampling in a medical intensive care unit. Random assignment was performed using an internet randomization service. The primary outcome was oral health status. Data were collected during May and June 2013. Participants were randomized to one of two groups (23 intervention and 21 control). The final analysis included 18 patients with combination oral care and 17 in the control group. The intervention group had better oral health (effect size = 1.56), less dry mouth and higher salivary pH than the control group. Any additional burden of providing combination oral care to patients who are mechanically ventilated is worthwhile in terms of clinical outcomes.