The most loved person in the department of Quetzaltenango, Mario Camposeco reflect his technical prowess, leadership and goal-scoring instincts, anchored by his record as Xelaju's most famous captain and Guatemala's 4th-highest scorer in the national team.

Born in Quetzaltenango, he began his football career in 1938 playing for the local team América. He then joined the Xelajú club, becoming vice-captain in 1940 and later captain in 1941, helping the team become champions of the department of Quetzaltenango for 10 consecutive seasons (1940–1950).

In 1942, he was called up as a reinforcement for Club Social y Deportivo Municipal by coach Manuel Felipe Carrera to play against Atlante F.C. of Mexico, and in 1943 he was selected for the Guatemala national team. On March 10, 1946, during the Third Central American Football Championship (CCCF Cup), he scored against the Costa Rican national team in a 4–1 victory in San José., where he ended the tournament as a runner-up and the player with most goals with 5.

In 1948, he was part of a small team that won a friendly tournament commemorating Cuban Independence in La Havana, Cuba. He then participated in the Fifth and Sixth Central American and Caribbean Games, being silver medallist. At the time, he became Guatemala's second-highest scorer behind fellow national team member Carlos Toledo, with 23 goals, which remains the fourth-highest total of all time.

In June 1951, after a friendly match in Quetzaltenango, he was invited by a friend to join him in a small plane to fly over the city; there was a mechanical failure and the plane crashed, killing both the pilot and Camposeco. After the footballer's death, the Xelajú Club of Quetzaltenango changed its name to "Xelajú Mario Camposeco" in his honor. The team's stadium was also renamed Estadio Mario Camposeco in his honor in 1957.