Although technology-supported writing instruction (TSWI) has received increasing attention, few review studies have investigated the application status, overall effectiveness, and moderating factors of diverse technologies in writing instruction. This study presents a systematic review and meta-analysis of research conducted over the past decade on TSWI in K–12 and higher education settings to investigate the effect of technologies on writing instruction. A total of 166 articles were selected from the Web of Science Core Collection database and analyzed in terms of technological features, instructional design, and research design. The results revealed that a range of technologies have been applied in writing instruction, with computers and auxiliary tools being the most commonly used types of hardware and software. Regarding instructional design, most technology has primarily been used to support challenging writing tasks, such as argumentative and foreign language writing. Due to the complexity of writing instruction, most interventions were one-time studies but had a longer duration, which effectively overcame potential novelty effects. The results of the meta-analysis revealed an overall medium positive effect (g = 0.648) for TSWI. Finally, we discuss the results and propose recommendations for technology developers, teachers, and researchers to foster future advancements in TSWI.