This paper tests for the sensitivity of R&D to financing constraints conditional on restrictions in external financing. Financing constraints of firms are identified by an exogenously calculated rating index. Restrictions in external financing are determined by (i) the specific time period (crisis vs. non-crisis) and (ii) the balance sheet strength of the firm’s main bank in terms of bank capital. Results of difference-in-differences estimations utilizing three time periods: 2002-2006 (pre-crisis) 2007-2009 (crisis) and 2010-2012 (post-crisis) support the theoretical prediction that financing constraints affect R&D. Moreover, we find that the effect of firm financing constraints is more intense (i) in times of stress on financial markets and (ii) when the firm faces restrictions in external financing. Additionally, our results indicate that on average the effect does not persist over time.