The current study aimed at the comparative effect of inter-sentential vs intra-sentential code-switching on learning past tense. Initially, through non-random convenient sampling, the researcher chose 90 female EFL learners at the elementary level. Next, Key English Test (KET) was administered to the 90 learners and the results were used to select 60 participants for the purpose of this study. The participants were then divided into two groups each consisting of 30 learners. Afterwards, a grammar pretest having 30 items focusing on past simple tense was given to both groups. Following that, the grammatical explanations were provided for the two groups for ten sessions using code-switching.  The first experimental group received inter-sentential code switching in line with Reyes’s (2004) as a switch between two languages, where a sentence in one of the languages is completed and the next sentence starts with the other language (Reyes, 2004). In the second experimental group, in line with Reyes’s (2004), the switching occurred within a sentence. The results of statistical analysis indicated that inter-sentential code-switching proved more effective compared to intra-sentential code-switching on the learning of past tense by EFL learners. Based on the findings of the present study, EFL teachers are encouraged to use inter-sentential code-switching more compared to intra-sentential code-switching when it comes to teaching grammar.