Mercury is the planet of communication, while Venus is the planet of love, romance, and affection. As such, when a Mercury-Venus aspects shows up in your synastry, the two of you enjoy sharing ideas and communicating with one another.
In the case of harmonious aspects (conjunction, trine, and sextile), the two of you are attuned to each other’s emotional sides. It is likely you two enjoy the same kinds of movies and music. This aspect also indicates you have mutual friends, and enjoy participating in social activities together. The way you speak to each other is kind, gentle and considerate. In fact, the Venus tends to soften Mercury’s analytical, overly-logical method of communication. Mercury helps Venus verbalize her feelings. This makes it easy to deal with conflicts.
Hard aspects (square, opposition) from Mercury to Venus can be a bit more tricky. Mercury is logical and unemotional, while Venus is romantic and fun-loving. Thus, the Mercury person may misunderstand the Venus person’s feelings, while the Mercury may see the Venus person as superficial or overly sensitive. When the Venus person feels romantic, the Mercury person feels logical and unemotional. As such, it can be difficult to communicate about emotional issues. In short, there is a fundamental lack of understanding of each other’s feelings. In addition, there may be differences in musical or cultural tastes, and you may have differing interests.
In one of my relationships, my Mercury in Capricorn squared my partner’s Venus in Aries. As the Mercury person, I tended to easily offend him. Mercury in Capricorn is reserved and shy when it comes to communication, especially when it comes to communicating about emotions. Being a Venus Aries, he was extremely puzzled and confused by my apparent “coldness,” and by the fact that I wasn’t verbally demonstrative with my feelings. When I actually did communicate my feelings, it still didn’t satisfy him, as the way I communicated wasn’t in a style he understood. We both felt the other was self-centered, due to the fact that we were constantly cutting in while the other person was speaking!