In this longitudinal study, we investigated the factor structure and stability of early-life temperament in a German sample, using three measures developed within Rothbart's psychobiological approach. Temperament was measured using the Infant Behavior Questionnaire Revised (IBQ-R) at the ages of 6 and 12 months, the Early Childhood Behavior Questionnaire (ECBQ) at the age of 18 months, and the Child Behavior Questionnaire (CBQ) at the ages of 36 and 48 months. We assessed longitudinal stability on a scale and factor level using data from the 85 participants that took part in each measurement. The latent factor structures were analyzed at each time point using all available data, ranging from 112 to 148 participants. Modest to high degrees of stability for most scales and all three latent factors was found. Stability was highest between measurements employing the same instrument and increased with age, indicating a consolidation of temperament traits over time. Model fit for the proposed factor structure consisting of Surgency, Negative Affect, and Effortful Control/Regulatory Capacity was poor, while exploratory factor analyses revealed similar but not identical structures for each time point. The third factor of Regulatory Capacity was not found at 6 months, but at 12 months and later, as is commonly the case in German samples. These findings further contribute to our understanding of the early development of temperament and its stability from infancy and beyond as well as expand on previous literature regarding its structure in German culture.