Purpose: The present research was based on an online questionnaire. A total of 256 undergraduate psychology students aged 18-44 (M = 23.61; SD = 0.57) from the Pontifical Catholic University of Argentina took part in the study (137 women; 53.3%). A sociodemographic and academic survey and the locally adapted versions of the Zimbardo Time Perspective Inventory (ZTPI), the Motivated Strategies for Learning Questionnaire (MSLQ) and the Tuckman Procrastination Scale were used in this study. Participants were contacted by an email advertisement in which the main purpose of the study was explained, and the instruments remained open from September to November of 2021. Descriptive analyses -- means, standard deviations and frequencies -- were calculated using IBM SPSS v.25, and mediation and moderation analyses were conducted on PROCESS macro. Design/methodology/approach: Academic achievement has always been a concern in the high undergraduate's community. Numerous studies have addressed psychological aspects of students' academic life; however, a past-positive (PP) time perspective, a warm and sentimental view of past events that took place in someone's life, has not been profoundly contemplated. The fact that students might organize their activities, employ different strategies to fulfill their tasks and motivate themselves to pursue their academic goals based primarily on their past experiences calls the attention on conducting research on this time perspective dimension and its relationship with procrastination and academic motivation. It was hypothesized that the PP time perspective would positively predict academic achievement via the mediation of academic motivation in a way that the potentiate effect of PP time perspective on academic achievement would be increased in highly motivated students, but this effect would be reduced in less motivated students. Also, it was hypothesized that the relationship between motivation and academic achievement would be negatively moderated by procrastination such that academic achievement would increase with academic motivation; however, that increase would be attenuated by procrastination. Findings: Academic achievement was positively associated with PP time perspective (r = 0.39; p < 0.01) and academic motivation (0.36; p < 0.01) and negatively associated with procrastination (r = -0.15; p < 0.05). Results showed that academic motivation mediated the relationship between PP time perspective and academic achievement ([beta] = 1.37; R[superscript 2] = 0.21; p < 0.001). Additionally, procrastination moderated the relationship between academic motivation and academic achievement but only at the low ([beta] = 0.76; p < 0.001) and medium ([beta] = 0.44; p < 0.001) levels of procrastination, while at high levels of procrastination, that relationship was not statistically significant ([beta] = 0.11; p > 0.05). Originality/value: This is the first study that examined the mediated role of academic motivation in the relationship between PP time perspective and academic achievement and that included the moderating role of procrastination.