Overstock.com Inc came last out of the 40 largest online retailers, with a rating of 72 out of 100, down 4 points from last year, the survey by ForSee found.
Customer satisfaction is important for retailers because it can lead to higher sales, more loyalty and increased word-of-mouth recommendations, ForSee said.
Netflix saw the biggest decline in customer satisfaction in ForSee's most-recent survey after the company tried to raise prices and split its DVD and video-streaming services. The plan was scrapped after customers defected.
"Netflix totally misread its customer base and is paying the price, damaging its brand among both consumers and investors," said Larry Freed, chief executive officer of ForSee.
Netflix shares lost more than half their value this year, with most of the damage coming after the company unveiled its intention to split its services.
Netflix had come close to customer-satisfaction leader Amazon.com in previous ForSee surveys. But in the latest poll, Netflix dropped 7 points to 79, the largest decline of any retailer in the survey.
Amazon climbed 2 points to 88 to lead ForSee's survey for the 14th consecutive time. ForSee runs the poll about every six months.