This study examined the use of first language in English reading lessons and the perceptions of teachers and students towards it in three Hong Kong Chinese-medium secondary schools. The data comprised three teachers and sixty-three Form 2 students' participation and responses in (i) 3 classroom observations about how L1 was used in actual teaching and learning settings, (ii) survey forms gathering the frequency of participants using L1 teaching and learning strategies (based on the three teachers and nineteen selected students from the pool), and (iii) subsequent in-depth interviews concerning their perceptions about using L1 in English reading lessons. The findings revealed that (i) the use of L1 bottom-up language focused teaching strategies and condition-oriented teaching and learning strategies were effective for teaching and learning in English reading lessons and (ii) there was a negative relationship between students' proficiency in English and the use of L1. The study concluded that the use of first language in English reading lessons brought positive effects on the second language learning in English reading, especially when students' English proficiency and teaching contexts were taken into consideration. Copyright ©International Journal of Instruction.