The purpose of the current research was to extend the Extended Parallel Model (EPPM) by adding the variable of barrier from Health Belief Model (HBM) to EPPM. The study explored the role of threat, efficacy, and barrier on participants’ attitudes and intentions towards exercising and eating a healthy diet for their heart health. A 2(threat)x 2(efficacy)x 2(barrier) x2(message replication) mixed factorial design experiment was conducted online via Amazon MTurk. The threat x efficacy x barrier was a between-subject design whereas message replication was within subject design. The stimuli messages were narratives about exercise and healthy diet behaviors. The result showed that there was a statistically significant main effect of barrier on participants’ perceived self-efficacy regarding exercise behavior but not for healthy diet behavior. As hypothesized the participants who read a message that addressed the barrier of time to exercising reported higher self-efficacy about exercising than the participants who read a message that did not address the barrier. Although a significant interaction between threat and efficacy was found on attitudes towards healthy diet behavior, the interaction was not in the predicted direction. No interaction between threat and efficacy was found on attitude towards exercise. Also, no interaction between threat and efficacy was found on intention to exercise or eat a healthy diet. A marginally significant effect of efficacy was found on attitude toward exercise, where participants who read a high efficacy message had more positive attitudes towards exercise than the participants who read a low efficacy message. The study found no interaction between threat and barrier on perceived self-efficacy, attitude, intention for either exercising or healthy eating behaviors. However, there was a marginally significant main effect of barrier on intention to exercise. Participants who read a message that addressed the barrier of time to exercise reported higher intentions to exercise than those who read a message that did not address the barrier. No three-way interaction of threat, efficacy, and barrier was found on attitude or intention to either exercise or eat a healthy diet. However, an interaction between efficacy and barrier on participants’ attitudes toward exercise was found. The result showed that participants who read a high efficacy message that did not address the barrier had the most positive attitude toward exercise followed by those who read a low efficacy message that address the barrier. This is an important finding suggesting that it is not necessary to address the barrier when the message efficacy is high. The study used narratives as message stimuli and found that the participants tend to identify themselves more with the characters in the high efficacy message conditions than the low efficacy message conditions. The findings suggest that addressing an individual’s perceived barrier regarding a health behavior may lead to an increase in their self-confidence about their ability to follow the recommended action. Some interactions of barrier with threat and efficacy on outcome variables were also found. These findings indicate that adding the concept of barrier to EPPM may increase the persuasiveness of the model. Future research should explore this extension of EPPM in other health behaviors to better understand how the variables threat, efficacy, and barrier work independently and interact with each other to influence individuals’ health decision making.