In this study we examined language learners’ attentional processing of a target syntactic construction in written L2 input in different input conditions, the change in learners’ knowledge of the targeted construction in these conditions and the relationship between the change in knowledge and attentional processing. 100 L2 learners of English in Sri Lanka were divided into four experimental groups and control group: input flood, input enhancement, a specific instruction to pay attention to the target grammatical construction in the input, and an explicit metalinguistic explanation of the target construction. Eye tracking was used to collect data on the attentional processing of 45 participants in the sample. The eye-tracking measures of learners who received a specific instruction to pay attention to the target structure and an explicit metalinguistic explanation indicated increased attentional processing. The learners in these groups also improved their knowledge of the target structure significantly. The results suggest that increased attentional processing is needed for development in L2 grammatical knowledge and that explicit instruction to pay attention to the input and metalinguistic explanation are successful in directing learners’ attentional resources towards novel grammatical constructions in the input.