This study aimed to determine non-native speakers of English academics' knowledge and awareness of conventions and norms of academic writing (AW), to develop an online professional development model addressing all disciplines, and to evaluate the effect of this model on their AW performances with their views on the model. The study was based on the mixed methods evaluation design. The participants were nine academics in educational and social sciences at a state university in Turkey. An online professional development model encompassing eight themes related to AW was developed. Data were collected through pre- and post-tutorial semi-structured interviews and writing tasks. Textual and content analyses were used for the qualitative data, and the Wilcoxon Signed Rank Test was performed for quantitative analysis. The results showed that before the tutoring, the participants acknowledged various difficulties regarding AW conventions and norms. The data after the online asynchronous tutoring showed that explicit instruction increased the participants' knowledge and awareness, and the proposed model contributed to their writing performances, and promoted their AW skills. However, participants' hedging use was found limited to modal verbs use. Paraphrasing tasks also showed significant differences between before and after tutoring writing tasks. Participants highlighted the importance of long-term implementational writing instruction.