Science journalists are responsible for the mass media’s representation of life sciences (e.g. biotechnology, genetics, and nanotechnology) and for the depiction of research findings in these areas as more scientifically (un)certain. Although researchers have determined that the representational styles of scientific evidence vary among science journalists, the reasons for these differences have not yet been fully investigated. Against this background, for the first time, the present study applies a reasoned action approach and investigates the predictors of the journalistic intention to represent scientific uncertainty, using computer-assisted telephone interviews with a representative sample of German science journalists (n = 202). The results indicate that beliefs about the coverage of other media, perceptions regarding scientific uncertainty of the main field of coverage, perceived expectations of the audience, past behavior, and gender were the predictors that most strongly affected the journalists’ intention to represent life sciences as more scientifically uncertain.