The goal of teaching the reading skill is to improve achievement for learners, yet the learners' reading comprehension test results in Kenya remain a challenge that requires appropriate intervention strategies. Previous studies have shown that pre-reading activities are facilitative pedagogic strategies that activate readers’ prior knowledge, hence comprehension of new text. Thus, the purpose of this quasi-experimental study was to establish if pre-reading activities had a significant effect on reading comprehension performance in selected secondary schools in Kenya. The study objectives were to assess if there was a difference in performance between learners that used brainstorming and those that used pre-teaching vocabulary; determine if pre-teaching vocabulary and brainstorming have a significant effect on the performance of English as Second Language (ESL) learners in reading comprehension; and, compare the effect of pre-teaching vocabulary and brainstorming on achievement in reading comprehension to determine which of the two pre-reading activities affects the performance of learners in reading comprehension more significantly. The study was underpinned by Reading Comprehension as a Socio-cognitive Processing Model by Ruddell and Ruddell; and Reading Comprehension as Transactional-Socio-Psycholinguistic Model by Goodman. These models respectively propagate the view that through the influence of the language teacher on the readers, and the individual transactions between a reader and the text, meaning is constructed. The study used a quasi-experimental group design. Stratified and purposive sampling techniques were used to select 7 schools, 21 English second language classrooms and 21 language teachers. Data were collected using a reading comprehension test. These data were analyzed using one-way ANOVA. The results of ANOVA showed that at p< .05 value, both pre-teaching vocabulary and brainstorming had a significant effect on the performance of Kenyan English Second Language learners in reading comprehension tests, though pre-teaching vocabulary was comparatively more impactful than brainstorming. The study concluded that teachers need to pre-teach unfamiliar words and/or brainstorm topics in the new text since they are effective pre-reading pedagogic strategies. The study recommended that teacher trainers, relevant Ministry of Education agencies, language teachers, and learners vouch for the use of pre-reading activities as a pedagogic strategy for enhancing reading comprehension.