In this paper, we investigated Bianchi Type I magnetized cosmological model with cosmological constant in Rosen’s bimetric theory of gravitation by using the techniques of Letelier and Stachel. The nature of the model is discussed in presence as well as in absence of the magnetic field and cosmological constant. Our model exists and it never goes to vacuum if cosmological constant is not equal to zero and for finite value of cosmic time. In the presence of magnetic field, our model goes to vacuum when the cosmic time tends to minus infinity. Further in the absence of magnetic field the model exists if cosmological constant is negative and n lies between zero and half and our model is filled with dark matter if cosmological constant is positive and n is greater than half. It is realized that, in the absence of cosmological constant our model goes over to the vacuum model
