"The advantages are too small and in fact would limit choices FCA could have available in the future," Sergio Marchionne told CNBC on Wednesday.
"A deal with PSA would prohibit other deals and would create a concentration in Europe that would limit the choices available to FCA going forward. Considering the international panorama this is not a deal we should do," he added.
Reports of a possible merger between FCA and other carmakers have been widespread over the last year since Marchionne, who is also chairman of Ferrari, tried to woo rivals in a bid to scale up the business and share costs. There were high hopes for a merger with GM but that fell flat, as did possible merger talks with Toyota and Ford.
Earlier in March, Marchionne told a news conference at the Geneva Motor Show that there were no talks going on between FCA and PSA Peugeot Citroen.