Individuals dispositionally differ in their willingness to invest effort in obtaining their goals and in their tendency to show effort discounting. Indeed, self-reported Need for Cognition (NFC) and Self-Control (SC) correlate with behavioral measures of effort discounting or demand avoidance, respectively. Given that NFC and SC are moderately related, the question arises whether they share some common construct core being theoretically embedded within a broader model. Thus, the present study aims at specifying a core construct of Effort Investment, i.e., for self-reported dispositional differences in the willingness and tendency to exert effortful control. We conducted an online-study (N = 613, 70% female, age mean ± SD: 29.1 ± 10.8 years) with several questionnaires related to cognitive motivation and effort-investment including the NFC and SC scales. We found substantial correlations between the assessed traits pointing to a core construct of Effort Investment. Furthermore, we could show that the relationship of NFC and SC is specifically mediated via an aspect that can be conceptualized as goal-directedness. These findings have been replicated in a separate sample (N = 244, 72% female, age mean ± SD: 23.4 ± 4.3 years). Taken together, our results extend our current knowledge on traits related to Effort Investment and provide a basis for further research on the role of dispositional individual differences in goal-directed behavior.