Early life and high school
Anthony was born in the Red Hook projects in Brooklyn, New York City. His father, Carmelo Iriarte, was born in Manhattan to Puerto Rican parents. Iriarte was of African, Spanish, and Indigenous ancestry; some of his roots also traced to Venezuela. His mother, Mary Anthony, is African-American. Iriarte died of cancer when Anthony was two years old. When Anthony turned eight, his family moved to Baltimore, where he honed not only his athletic skills, but his survival skills. Kenny Minor, one of Anthony's childhood friends, said, "from drugs to killings, to anything you can name that goes on in the roughest parts of town, we've seen and witnessed hands on. Those are the things that teach you toughness and keep you mentally focused on your goals." Sports would serve as an important diversion from the violence and drug dealing that were pervasive in the housing projects a few blocks from the homes of Anthony and his friends.
Anthony commuted to Towson Catholic High School for his first three years of high school. During the summer of 1999, Anthony grew five inches into the frame of a 6–5 swingman. He suddenly became one of the area's top players and made a name for himself in the area, being named The Baltimore Sun's metro player of the year in 2001, as well as Baltimore Catholic League player of the year. During his sophomore year, he averaged 14 points, 5 rebounds, 4 assists and 2 steals. Towson Catholic surged to a record of 26–3 and finished third in the state tournament. Anthony enjoyed a successful high school basketball career as a junior, almost doubling his numbers in scoring and rebounds, averaging 23 points and 10.3 rebounds. Despite his successful year, Anthony was distracted by all of the attention, and was suspended on several occasions for skipping classes. He barely registered a blip on the radars of pro scouts with his skinny frame and lack of strength; many scouts felt that he was not ready for the physical demands of the NBA. In the end, Towson Catholic fell short of the state title, although he was named Baltimore's County Player of the Year, All-Metropolitan Player of the Year and Baltimore Catholic League Player of the Year.
After his junior year, Division I coaches were lined up to recruit Anthony to a school on the East Coast, which included North Carolina and Syracuse. In contrast to contemporary prep-to-pro players like Kevin Garnett, Jermaine O'Neal, Kobe Bryant, Tracy McGrady or Amar'e Stoudemire, he decided to declare early and announce that he would attend Syracuse University before his senior year. As Anthony's grades dropped under a C average and his scores on the ACT were below acceptable standards, he knew that he needed to improve in the classroom to qualify academically for Syracuse. For his senior year, his mother considered transferring him to a different school. Anthony first thought of Virginia's Hargrave Military Academy but after talking to Steve Smith, the head coach at basketball powerhouse Oak Hill Academy, he eventually transferred to Oak Hill Academy in Virginia—winner of the USA Today 2000–01 high school championship—for his senior campaign. During the summer of 2001, Anthony led an AAU Baltimore Select team to the Final Four of the Adidas Big Time Tournament in Las Vegas, Nevada. Anthony attracted attention from the NBA by averaging 25.2 points a game in the tournament, which was also attended by Amar'e Stoudemire (who was already being touted as a future lottery pick). Anthony played at the USA Basketball Youth Development Festival where he helped the East Team win the silver medal. He tied LeBron James for the tournament scoring lead at 24 points per game and shot 66 percent from the field. It was there that Anthony and James struck up a friendship.
Oak Hill Academy entered the 2001–02 campaign boasting a 42-game winning streak. The team's first tournament win came in The Les Schwab Invitational against Mater Dei High School from Santa Ana, California, with Anthony winning the tournament MVP. Oak Hill won two more big-time tournaments, including the Nike Academy National Invitational where they knocked off then-No. 1 Westchester High School 77–61 in the final, and an anticipated game against St. Vincent – St. Mary High School of Akron, Ohio, where he was matched up with high school phenom LeBron James. James scored 36 points, while Anthony scored 34 points and grabbed 11 rebounds to lead Oak Hill to a 72–66 win. The team ended the season ranked third in the country at 32–1, with their only loss coming in a rematch against Mater Dei, which ended their unbeaten streak at 67. He averaged 21.7 points, 8.1 rebounds and 4.0 assists during his senior year at Oak Hill and named a USA Today All-USA First Team and a Parade First-Team All-American. He was selected to play in the Jordan Brand Classic, scoring a game-high 27 points, and the 2002 McDonald's All-American Game, where he played on the same team with two future New York Knicks teammates, Raymond Felton and Amar'e Stoudemire. In that game, he scored 19 points and won the Sprite Slam Jam dunk contest. His performances at the high school All-Star games, helped lift his reputation with HoopScoop ranking him as the nation's No. 1 high school senior in the class of 2002, ranked 2nd by College Basketball News and 3rd by All-Star Sports. Due to his struggles with the ACT, his family and friends wondered whether Anthony would forget about his college plans to attend Syracuse and move on to the NBA. He had yet to produce the minimum score of 18; however, in late April Anthony got a 19 and decided to stick with college and prepared for his freshman year at Syracuse. In April 2009, he was named to the ESPN RISE's all-decade team and was honored as one of the 35 Greatest McDonald's All-Americans in January 2012.