The present study investigates the effects of online collaborative writing instruction combined with metacognitive guidance on students' writing performance in German as a foreign language and their metacognitive awareness. For this purpose, a total of 90 students are randomly and equally divided into three groups: group with online collaborative writing instruction combined with metacognitive guidance (on-CWI+MG), group with face-to-face collaborative writing instruction combined with metacognitive guidance (f2f-CWI+MG) and group with in-class individual writing activities without metacognitive guidance (i-WRITE). Results revealed that the on-CWI+MG group showed the best writing performance and there was a complex interaction with the f2f-CWI+MG group in terms of metacognitive awareness. Moreover, the two basic levels of metacognitive awareness, knowledge about cognition and regulation of cognition, had a predictive effect on writing performance, with knowledge about cognition having a larger effect. Relevant implications for better understanding online collaborative writing instruction combined with metacognitive guidance are discussed.