This research proposed a situational learning system to help elementary school students practice and improve their English as a foreign language (EFL) writing skills. Students carried out assigned writing tasks using the support of mobile devices in situations deemed to be familiar to the students, such as on the school playground, within classroom facilities, and at lunch. The study recruited 59 sixth-grade students from two separate EFL classes. A class of 28 students was identified as the experimental group, and another class of 31 students was assigned as the control group. The students of the experimental group carried mobile devices to carry out EFL writing assignments within specific and familiar subject environments, stimulating real-life situations or contexts. The results of the experiment indicated a significant difference in learning achievement between the two groups. Students in the experimental group perceived the designed activities to be fun; thus, they were more inclined to maintain interest in situated learning scenarios. Furthermore, based on interviews with participating students from both groups, we found that the activities presented within familiar contexts, and supported by our proposed EFL writing system, inspired students to not only write more sentences, but to describe the target objects clearly and thoroughly.