The present study investigates the writing performance in terms of language complexity, accuracy and fluency (CAF) and the pupils' perceptions of their performance under different planning conditions and the relationship between pupils' perceptions and their performance. There were 78 ESL pupils from a Chinese primary school in Malaysia who were grouped into three planning conditions:1) pre-task planning, 2) on-line planning and 3) no planning groups. This study employs a variety of data collection methods that include the collection of pupils' written tasks and questionnaire surveys. The results of the study indicate that planning conditions did not have a significant impact on pupils' writing performance except for the effect of pre-task planning on pupils' written fluency. The results also differ greatly from numerous previous studies, which have been mainly conducted on adult writers. The present study also shows that pupils' perceptions are partially related to their writing performance. The reasons for such contradictions are discussed. The findings have implications for the teaching of writing in the ESL context. Keywords: second language writing; planning conditions; narrative writing task; primary school ESL learners; writing processThe task of writing can often be challenging for ESL learners because of the different mental processes involved. However, the task of completing a piece of writing can be even more demanding for young ESL learners, whose English language proficiency is still developing. It is argued that young ESL learners' limited range of vocabulary and basic mastery of grammar can affect their writing performance (Nam, 2011). Confusion between school and home environments, cultural backgrounds, and underdeveloped bilingualism are among the factors that affect young ESL writers' proficiency (Nam, 2011). Because of this, their writing may not reflect the complexity of mature writers. When they write, they tend to rely on any linguistic resource available to them and their writing could be characterized by spelling and letter forms that are invented and unconventional, inaccurate segmentation and punctuation and the expression of ideas through drawing or writing (Hudelson, 1989).According to Kellogg (1996), planning is one of the mental processes that learners employ in their writing. Based on second language acquisition (SLA) literature, planning can be categorised into two types: 1) pre-task planning and 2) on-line planning. These two types of planning differ in terms of the provision of time to learners. In pretask planning, time is allocated to learners before the actual performance of a task (Johnson, Mercado & Acevedo, 2012), whereas in on-line planning or within-task planning, the unpressured time limit is given to learners to perform pre-production and post-production monitoring (Ellis & Yuan, 2004). In the process of planning, learners usually engage in subprocesses such as idea generation, goal setting, and organisation (Johnson et al., 2012). In connection to this, Ellis...