A compass needle gets deflected when brought near a bar magnet because the compass needle itself is a small magnet. When it is brought close to the bar magnet, the magnetic field lines of the compass needle interact with the magnetic field lines of the bar magnet. This interaction causes forces of attraction and repulsion between the unlike and like poles of the needle and the bar magnet, respectively. As a result, the compass needle aligns itself with the magnetic field of the bar magnet, causing it to get deflected from its usual alignment with the Earth's magnetic field.

In essence, the compass needle responds to the stronger magnetic field of the bar magnet when it is nearby, overriding the Earth's magnetic influence at that location and leading to its deflection.