McMackin has coached extensively at both the collegiate and professional levels. At the professional level, McMackin has coached for two National Football League teams: as defensive coordinator for the Seattle Seahawks from 1995 to 1998, and as linebackers and assistant head coach for the San Francisco 49ers from 2003 to 2005. He also coached for the Denver Gold of the defunct United States Football League. At the college level, McMackin gained prominence as the defense coordinator for the University of Miami for the 1993 and 1994 seasons. There, Miami won two Big East Championships and ranked first in total defense, scoring defense and pass defense. Further, the Hurricanes allowed just seven touchdowns on defense in one season. While there, he coached Lombardi Award winner Warren Sapp, Ray Lewis and six First-Team Consensus All-Americans. The Hurricanes played in the national championship game in 1994. McMackin has served as defensive coordinator at six colleges: Hawaii, Texas Tech, Miami, Navy, Utah, and Idaho. Briefly, during the first half of the 2007 spring semester, McMackin was an instructor at Texas Tech. McMackin, previously the defensive coordinator for the Hawaii Warriors, was one of several individuals being considered to fill the vacancy left by June Jones as head coach. Jones left the Hawaii Warriors in January to become the head coach of SMU. On January 15, 2008, McMackin took over the position of head coach for the Hawaii Warriors. Upon signing his five-year contract, McMackin became the highest-paid state employee with a $1.12 million annual salary. The previous record was held by his predecessor, June Jones, with an $800,016 annual salary. On August 1, 2009 McMackin was suspended for 30 days without pay due to his use of a homophobic slur during an interview. McMackin resigned from his position of head coach for Hawaii on December 5, 2011, accepting a $600,000 buyout.
In 1999, led the University of Hawaii's defense to help orchestrate the biggest single-season turnaround in NCAA football history
Named one of the nation's top coaches by American Football Magazine while at Texas Tech.
Named Big 12 Conference's top recruiter by Rivals.com
As the defensive coordinator for the Seattle Seahawks, coached seven All-Pro selections, and established a franchise-record for seven interceptions in one game. Overall, Seattle's defense improved from 30th to 8th.
As defensive coordinator for the University of Miami, McMackin's defense was ranked first in the nation in total defense, scoring defense and pass defense.
Both of Hawaii's WAC championships during former coach June Jones' tenure at Hawaii came during both of McMackin's two years as defensive coordinator for Hawaii.
Authored Coaching the Defensive Backfield in 1992, which is in its seventh printing.
