The present study examined the perception of English tense-lax vowel pairs by adult Saudi English as a second language (ESL) learners. More specifically, it looked at the effect of experience and length of exposure to the target language on the perception of these vowels. Thirty-eight male Saudi participants were recruited for the purpose of this study and were divided into two groups based on their level of proficiency and length of residence in the US, referred to as the experienced group and the inexperienced group, respectively. The research instrument contained four tense-lax vowel pairs, including /i/-/ɪ/, /e/-/ɛ/, /u/-/ʊ/, and /o/-/ɔ/. In order to control for the effect of the environment, all of the vowels were embedded in /hVd/ contexts as illustrated by the following examples: heed (/i/), hid (/ɪ/), hayed (/e/), head (/ɛ/), hawed (/ɔ/), hoed (/o/), hood (/ʊ/), and who'd (/u/). Native-speaker recordings of each vowel token were used to test participants’ perception accuracy. The recordings included both male and female voices. According to the statistics provided by the t-tests, there were significant differences in the perception of five out of the eight vowels that were examined in this study. In all five cases, the experienced group had a significantly better perception accuracy. The vowel that showed the highest magnitude of difference between the experienced and inexperienced students was the tense mid front vowel /e/ with an effect size of 1.5. It was followed by the lax high back vowel /ʊ/ with an effect size of 1.08. The third in magnitude of difference was the lax mid front vowel /ɛ/ (effect size = 1.02), followed by the lax mid back vowel /ɔ/ (effect size = 0.79), and finally the tense mid back vowel /o/ (effect size = 0.72). On the other hand, vowels that did not show significant differences between the two groups were the tense and lax high front vowels /i/ and /ɪ/ and the tense high back vowel /u/. However, although the experienced group showed a significantly higher level of perception accuracy in five out of the eight tense-lax vowel contrasts, the participants in this group reached the 80% accuracy level with only two vowels: /i/ and /e/. On the other hand, the inexperienced group did not show mastery of any of the eight vowels as their perception accuracy scores were below 80%. In terms of related theories, some of the results supported the Perceptual Assimilation Model (Best, 1994), the Speech Learning Model (Flege, 1995), and the Markedness Differential Hypothesis (Eckman, 1977), whereas other findings provided contradictory evidence. Overall, this study concluded that experience and exposure had a positive effect on Saudi ESL speakers’ perceptions of the tense-lax vowel contrasts in English. Even though this effect was not the same for all vowel contrasts, it carried the implication that perception accuracy can be facilitated through systematic training and practice.