In Turkey, first-year preservice English teachers learn L2 writing in at least two compulsory courses throughout their undergraduate ELT [English Language Teaching] programs. This study, conducted in this context, intends to investigate preservice English teachers' perceptions about L2 undergraduate writing difficulty and their causal attributions for these difficulties. It also aims to examine the relationship between density/variety of perceived difficulty in L2 writing and writing scores. For these purposes, the case study approach was adopted. In order to answer three research questions, in-depth interviews were conducted with 26 first-year preservice teachers studying in the ELT department of a Turkish state university, and their first-midterm writing scores were collected. According to the findings, firstly all the interviewees agreed that students in the program had difficulty while writing in L2. Secondly, the correlational analyses revealed a negative relationship between density/variety of perceived L2 writing difficulty and writing scores. Lastly, three main sources of perceived writing difficulty were identified: 1) "student-based sources," 2) "educational practices and tendencies" and 3) "lecturer-based sources." After all, the related inferences, discussions and suggestions about learning and teaching of L2 writing have been addressed based on the current findings.