YouTube, the most popular present-day online video platform, is also considered one of today's leading advertising media. There is an ongoing argument that YouTube measures and shares its own ad effectiveness. However, the consumer research results contradict with their measurements. The difficulty of measuring the performance of video ads on YouTube without YouTube's built-in data increases the debate about its effectiveness as an advertising environment and therefore makes it more important to collect data from consumers through empirical research. This study was carried out with YouTube viewers located in Turkey, whose population is among the most online video watching Internet users in the world, to uncover the determining attitudes and the factors affecting them in the effectiveness of bumper ads, which YouTube introduced in 2016 as 6-seconds unskippable ad videos. The acquired data were tested by correlation and regression analysis under a predicted model that could explain the attitudes towards the ad. According to findings; it has been shown that the attitudes towards bumper advertisements are significantly related to the factors such as entertainment, informativeness, credibility, irritation, frequency of exposure and advertising value. However, it was found that the participants did not develop a positive attitude towards these factors, and the bumper advertisements, along with them.