Irritability and parenting are potential targets for transdiagnostic studies to identify the common and core dysfunctional characteristics underlying several diagnostic pictures with the goal of addressing these issues in treatment. Our objective was to investigate the different paths from temperament to child psychopathology (affective, anxiety, and oppositional problems) through irritability and parenting using a prospective design from ages 3 to 7. A sample of 614 3-year-old preschoolers was followed at ages 4, 6, and 7. Parents answered questionnaires about temperament (age 3), irritability (age 4), parenting practices (age 6), and psychopathology (age 7). Statistical analyses were carried out through structural equation modeling (SEM) to test the mediation effect of irritability and parenting practices from temperament (negative affectivity and effortful control) through to affective, anxious, and oppositional problems. The proposed model fit the data well. SEM showed (a) an indirect effect from temperament to affective problems, via irritability and positive parenting; (b) a direct effect from negative affectivity to anxiety, plus an indirect effect from both temperament dimensions, via irritability and autonomy parenting practices; and (c) an indirect effect from temperament to oppositional problems, via irritability and punitive parenting. Irritability and parenting are transdiagnostic mediational variables that should be focused on in intervention programs for affective, anxiety, and oppositional problems.