On-farm non-agricultural diversification is increasingly important for many farmers to stabilize their income and to fulfill societal demand for integrated farming. Especially in peri-urban areas, where the potential for farms' expansion in terms of farm size is limited and public interest in regional products and other services provided at farms is high, the uptake of on-farm non-agricultural diversification is thus an attractive strategy for many farmers. The here presented dataset is based on an online survey conducted in March 2016 with 156 farms located in the Ruhr Metropolitan region (North Rhine-Westphalia, Germany). The survey was used to collect information on farms' and farmers' characteristics. More specifically, the dataset includes detailed information on farms' diversification decisions, location, size and general information on farms' production type and structure. Moreover, the dataset contains information on farmers' risk perception and risk preferences (collected using three different elicitation methods) and general information on farmers and households. In addition, farmers' personal assessments on agricultural production in peri-urban settings and information on the use of extension services were collected.