Purpose This paper aims to analyze the portfolio characteristics and the performance measures of sustainability-themed mutual funds, compared to ethical mutual funds that implement different sustainable and responsible investment strategies. Design/methodology/approach The study refers to a European sample of 106 ethical funds and 51 sustainability-themed funds. The monthly performance of each fund is downloaded from Bloomberg for the period from January 1996 to December 2015. By applying a Fama and French (1993) three-factor model, the authors overcome the limits of a capital asset pricing model (CAPM) based-single index model, to compare the performance of the two categories of funds. Findings Sustainability-themed funds do not differ significantly from ethical funds in terms of portfolio attributes, except for market capitalization, age and net asset value. Regarding performance measures, the results shows that sustainability-themed funds have a lower underperformance than ethical funds (as measured by Jensen’s alpha), whereas the samples do not differ in terms of market risk (as measured by Beta coefficient). The idiosyncratic risk of sustainability-themed funds is positively influenced by the specific portfolio strategies. The sustainability-themed funds show a higher concentration in the industrial sector and a lower exposure to financial sector than ethical funds; in terms of geographical strategy, they are more global and international oriented; they mainly focus on small caps and value stocks. Research limitations/implications The different sustainable and responsible investment strategies can be applied simultaneously and in a growing number of possible combinations. Mutual fund managers can consider thematic approach as an efficient opportunity for reconciling financial performance and economic sustainability. It is demonstrated that sustainability-themed funds adopt a portfolio strategy significantly different from ethical funds and from the environmental, social and governance benchmarks. Mutual fund managers implement a thematic specialization without any negative impact on the funds returns compared to ethical funds; actually, with a proper diversified portfolio, they are able to reduce idiosyncratic risk. Originality/value The analysis is extremely innovative, especially for the thematic sample. During the past 15 years, literature about sustainable and responsible investment has been focused especially on the differences in terms of risk and performance between socially responsible and conventional funds. This paper, starting from the methodology applied in these studies, wants to compare two different types of socially responsible strategies, with a specific focus on sustainability-themed mutual funds, given their exponential growth in the past few years.