On Tuesday, her parents walked the 6-year-old back into the school as students and staff cheered.
As soon as she saw her teacher, Joselin ran into her arms and said, "I missed you!"
She was greeted by dozens of students at Peck Elementary School.
Joselin was born with one heart chamber and has courageously lived with Hypoplastic left heart syndrome, also known as HLHS.
After years of various treatments, and months of waiting for a donor, she underwent a successful heart transplant in July.
"She cried and prayed, every week she kept asking for her new heart. She's like 'I don't want to die here like my other friends'. So, we never knew she was going to walk into school," mother Jacqueline Martinez said.
Her teacher decorated the classroom with a "Bluey" themed episode called "Joselin's Big Return."
Joselin's family hopes this raise awareness about heart conditions and supports others in similar situations