This paper describes the main features of PIAAC-L, the German longitudinal follow-up to PIAAC (Programme for the International Assessment of Adult Competencies), and presents the PIAAC-L data. PIAAC-L was a collaborative study by three large-scale surveys in Germany, PIAAC, the National Educational Panel Study (NEPS), and the German Socio-Economic Panel (SOEP). RespondentS f~Om the German PIAAC sample (2011/2012) and the adult members of their households were interviewed over three waves (2014, 2015, 2016). PIAAC-L combined design features and instruments from PIAAC, NEPS, and the SOEP and included a re-assessment of basic cognitive skills. Literacy and numeracy were measured with instruments from PIAAC and NEPS and the assessment was extended to include cohabiting spouses/partners of PIAAC respondents. Interviewer-administered person and household questionnaires covered a broad range of content. The PIAAC-L data, which are available to researchers for secondary analyses, allow to explore cognitive skills over time and factors related to their acquisition and maintenance. In the German context, the study is of interest because it combined expertise and content from three national large-scale surveys.