The short answer is yes, and it worked. In my case I moved the antenna to the other side of a wall from where the base station sits. This only needed a short length of cable that was easily hidden. As walls (particularly double as mine is) are big attenuators of WiFi signals this gave a huge improvement in performance.
But the antenna itself also gives an increase in signal strength (not massive like the absence of a wall, but given your description you don’t need that anyway). A high gain antenna works by “directing” more signal energy into a narrow beam; they don’t “amplify” the signal. Thus, depending on where you want to pick up the signal, some areas may actually have a weaker signal then before. Just think of the antenna as a torch, while you are in the beam you are fine, go behind it, for example, and you could be in trouble.
And finally, you may make it easier for your neighbours to pick up the signal in the beam, so consider the usual WAP/WEP protection.