To date, few studies have emphasized the use of language learning strategies in the acquisition of L2 pronunciation, specifically those classified as cognitive and metacognitive strategies. Yet, there is a significant gap in the literature that this study attempts to fill, namely, the lack of descriptions of the acquisition of L2 Spanish diphthongs. This study draws upon various approaches, namely, cognitivist, constructivist, and sociopsychological, to shed light on the application of four language learning strategies (i.e., critical listening, repetition, rehearsal, and annotation) combined with Dickerson’s covert rehearsal model (CRM) to practice the pronunciation of Spanish rising diphthongs (SRD); that is, /ia/, /ie/, /io/, /iu/, ua/, /ue/, /uo/, and /ui/. Sixteen native English-speaking L2 Spanish learners were randomly assigned to experimental (n = 8) and control (n = 8) groups. A group of 8 native Spanish speakers provided baseline values of diphthong productions. Learners were recorded performing three tasks at pretest: a word list (Task 1), a Spanish text (Task 2), and an English sentence list (Task 3). An acoustic analysis of the first two tasks from the pretest and posttest was conducted with respect to three acoustic measures: (a) total duration of the diphthong, (b) duration of the three parts of the diphthong (i.e., Vowel 1, Vowel 2, and Transition), and (c) duration of individual diphthongs. An additional element of investigation in this study was the role of individual social factors, including motivation and attitude, as well as the linguistic factor, L1 dialectal variety. Quantitative results from learners who employed the self-monitoring strategies and CRM model (i.e., L2 experimental group) revealed statistically significant target-like achievement in the pronunciation of SRD with respect to all acoustic measures in Task 1, but not for Task 2. Correlation analyses suggested that extrinsic motivation was a potent factor affecting the pronunciation of SRD in both the L2 experimental group and L2 control group. Moreover, affective attitude was positively correlated with the target-like productions of SRD in L2 experimental group learners. Statistical examinations of the L1 learners’ dialectal variety and the pronunciation of SRD did not provide strong evidence in support of the effect of a specific L1 variety influencing the pronunciation of SRD in the L2 Spanish learners.