This paper presents the design of nose-cone conformal substrate-integrated waveguide (SIW) slot array antenna for modern radar applications. Firstly, the wave propagation characteristics have been investigated in doubly curved SIW, and it has been observed that they are non-uniform along the longitudinal direction of nose-cone conformal SIW. To ensure the constant wave propagation along the length of conformal SIW, the conventional design of SIW is reformulated for nose-cone conformal SIW and circuit model modification has been demonstrated. Secondly, the procedure for designing a SIW-based array on curved surfaces has been developed. In the proposed design, rectangular waveguide (RWG) to SIW feeding structure has been used to avoid spurious radiations. Finally, 1 × 6 element-based nose-cone conformal slotted array has been designed and compared with planar and cylindrical conformal arrays. It has been observed from the results that the nose-cone conformal slot array offers low sidelobe levels (SLLs) and high gain. For the validation of the proposed design, the conformal slotted array has been fabricated and measured, which exhibited a reasonable agreement between the measured and the simulated data.