Generally, no. While astrology has nothing to do with whether or not a god exists, most atheists don’t believe in it for the same reason that they don’t believe in the existence of a god – there is no evidence that astrology is true.
Astrology is a set of beliefs and practices around the idea that the events of everyday life are affected by the motions of stars, planets, and moons. The word ‘astrology’ comes from the Greek astron, meaning ‘star’, and logia, meaning ‘speech’. In Modern English, the suffix -logy is used for academic subjects – because of this, astrology is sometimes mistaken for one – but it’s not. The scientific study of stars, planets, and moons is astronomy.
Astrologers often believe that celestial events affect our day-to-day fortunes – whether we will be lucky on any given day, whether we will succeed or fail at the things we try to do. These aspects of life are very complicated, and there is no known physical mechanism by which celestial events could effect any of these things. To believe that there is is pure mysticism.
An atheist is someone who does not believe in the existence of one or more gods. They take this position because there is not sufficient evidence to prove that any gods exist. They maintain a position of scepticism. For this same reason, atheists generally don’t believe in astrology either – there is not sufficient evidence (indeed, there isn’t any evidence) to prove that astrology is true.
Don’t the planets have some effect on Earth, even if only a small one?
Technically, the other planets, moons, as well as all of the stars – everything in the universe – has some effect on the Earth and its inhabitants. Every mass in the universe is attracted to every other mass in the universe – this is, in simple terms, Newton’s Law of Gravitation. Thus, all of the planets in the solar system – Jupiter, Saturn – the lot – exert a gravitational force on the Earth, and on you. So does every star and galaxy in the universe. However, this force is so small you could never measure it. And while it does exist, it could never affect your life in a complex way.
A minor exception is the Moon. The Moon does exert a measurable force on objects on Earth due to gravity – that’s in part why we have tides – the water of the Earth is pulled around by the Sun and the Moon. However, again, this force could not affect your life in a complex way (unless you get caught in a high tide).
Another way that the stars could affect your life is if a nearby star underwent a supernova. If the star were close enough, it would be like having a second sun in the sky for a few days or weeks. So it would affect your life in that it might keep you awake at night, but that’s about it. This isn’t what astrologers usually mean by their beliefs.