The attack became known when a co-worker told superiors about it.
According to the local newspaper Helsingborgs Dagblad (HD), the colleague witnessed the nursing assistant go into a cleaning closet and pick up a broom.
The nursing assistant then used the broom to push the patient's wheelchair before then beating the patient's head and face with the broom.
"I've worked in this business for many years, but I've never heard of anything like this," said Båstad's head of healthcare Susanne Hertting to HD.
Skogsliden's management reported that there was nothing to suggest the patient was injured, but a medical examination has been ordered.
This isn't the first time Skogsliden has come in for heavy criticism, according to HD.
The National Board of Health and Welfare (Socialstyrelsen) criticised the home last year, pointing out several unacceptable flaws, such as insufficient staff and patients who weren't allowed to shower when they wanted to.
However, Hertting doesn't think events of the past week have anything to do with previous flaws.
"This is about one single person. We know that most of our staff do a fantastic job. No matter how hard work gets, or if you're angry at your boss, you don't go and hit an innocent person," she said to HD.
The nursing assistant, who is also suspected of stealing medicines, has been suspended, wrote HD.