The present study was an attempt to determine the effectiveness of using a WhatsApp Messenger as one of mobile learning techniques to develop students' writing skills. Participants were 30 second year college students, English department from a private university in Saudi Arabia. The experimental group (N = 15) used WhatsApp technology to develop their writing skills; whereas the control group (N = 15) was taught their writing skills through prescribed book. The pre-post test comprised three questions, punctuate a paragraph, correct a paragraph and write an essay. This research is limited to punctuation marks, sentence structures and generating ideas. Results of the "t-test" analysis revealed that WhatsApp technique yielded significant effects on students' writing skills, i.e. the experimental group outperformed the control group.