Lieutenant commander Lieutenant commander was a commissioned officer rank , the equivalent of which is used by the service organizations of many civilizations . Origins and history . A traditional naval rank , lieutenant commander was once used in the old navies of Earth , among them the Royal Navy and the United States Navy . In these organizations , a lieutenant commander was a grade between the lieutenant and commander grades with the rank equivalent to a major in the marine or ground forces . In the mid 2160s , Starfleet was using the rank of lieutenant commander . ( ) In the early 2260s , the rank of lieutenant commander was being used by the Starfleet of the United Federation of Planets . The insignia was at first the same as that of lieutenant , but by 2266 had developed into its own design . 23rd and 24th century usage . During the 23rd century , certain lieutenant commanders holding high shipboard positions , such as that of first officer , in a military tradition known as " brevetting " , were authorized to wear the full braid insignia of a commander while still retaining their rank of lieutenant commander . ( ) In the 24th century Starfleet , lieutenant commander is an active rank with its close equivalents in alien militaries being the Cardassian rank of glinn and the Romulan rank of centurion . It is common in informal circumstances to refer to lieutenant commanders in Starfleet simply as " commander " by both those under their command and their commanding officers . Lieutenant commanders normally serve as senior department head s , executive officers on smaller vessels , and in some cases as starship commanders . Lieutenant commanders Tom Markel , Jadzia Dax , and Piersall all held commanding officer postings . It is worth noting that Jadzia Dax served as the commanding officer of the during the height of the Dominion War because she had acted as Captain Sisko ' s second in command and was the most qualified to take over for him when he had been reassigned to administrative duties at a starbase . However , her posting was temporary until the Captain returned to command a taskforce during Operation Return . ( ) Another position that could be held by a lieutenant commander was as an instructor for Starfleet ' s Advanced Tactical Training . ( ) The rank of lieutenant commander is also known to have existed in parallel universe s . In the mirror universe , the Terran Empire Starfleet was using this rank in 2155 ( with T ' Pol being an example ) and the rank was still being used in 2267 . ( ; ) Regarding the service record of Ensign Ro Laren , as of 2369 , Jean - Luc Picard explained that " " if she hadn ' t lost her rank in that incident at Garon IV , she ' d be Lieutenant Commander by now . " " ( ) Commander William T . Riker read , during the mock sentencing staged for the promotion of Lieutenant Commander Worf , in 2370 : " " We , the officer s and crew of the , being of sound mind and judgment , hereby make the following charges against Lieutenant Worf . One . That he did knowingly and willfully perform above and beyond the call of duty on countless occasions . Two . Most seriously , that he has earned the admiration and respect of the entire crew . " " Following the reading of the " charges " , Captain Picard granted Worf his new rank , " " with all the rights and privileges thereto . " " ( ) Appendices . Background information . The earliest known Starfleet officer with this rank is Hoshi Sato , as established in a biography shown in . There have been four clear instances in " Star Trek " where a Lieutenant Commander was verbally addressed as " Lieutenant " : Likewise , Tuvok was also incorrectly identified as Lieutenant after his promotion to Lieutenant Commander during his travels in the Delta Quadrant . Conversely , he was frequently seen wearing Lieutenant Commander ' s pips during the first season despite holding the rank of Lieutenant at the time ; this appears to have been a costume error or possibly a sign that the decision to make him a Lieutenant was made after shooting started . On a similar note , apparent costuming errors throughout had Valeris wear Lieutenant Commander insignia ( as well as mismatched uniform department colors ) , although the intention was to have her just hold the rank of Lieutenant . Because it was deemed too expensive to go back and reshoot the sequences with Valeris wearing the correct rank and uniform color so it was decided to just let it be . An issue of established that the costuming department on had no insignia for lieutenant commander . However , this does not mean the rank did not exist , merely that no on screen character had it and that no episode called for it . The rank was originally considered for use on the show with Malcolm Reed intended to be a lieutenant commander . In " Enterprise " Season Four episode , Commander Tucker refers to his replacement " Kelby " as lieutenant despite him wearing three pips .