In this work, we study a class of Kirchhoff-type equations with indefinite nonlinearities of the form \(-\left( 1+\lambda \int _{\mathbb {R}^3} |\nabla u|^2\right) \Delta u = f(x)|u|^{\gamma -2}u\) in \(\mathbb {R}^3\) , where \(\lambda >0\) is a parameter. Using variational methods and a simplified version of the concentration-compactness principle, we overcome the lack of compactness inherent to the unbounded domain. Under suitable conditions on f, we provide a precise description of the bifurcation phenomena occurring with respect to the parameter \(\lambda \) . We show that there exists an extremal parameter \(\lambda ^*\) which acts as a turning point where two branches of solutions collapse and vanish. Our results generalize previous studies by removing the boundedness condition on the domain and considering sign-changing nonlinearities.