Ensign Janeway graduated from the Academy and was assigned to Admiral Paris's staff in San Francisco in 2357. At Paris's request, Janeway assisted civilian advisor Kyle Riker uncover the involvement of Vice-Admiral Horace Bonner in the Tholian attack on Starbase 311 in 2353, as well as several attempts on Riker's life.
Tired of sitting behind a desk, Admiral Paris made the decision to get back into the game and arranged to be in command of the USS Al-Batani for the year-long Arias expedition. Admiral Paris asked Janeway to join his crew as junior science officer. (TLE novel, Deny Thy Father; Mosaic).
Note: The novel Mosaic states that Janeway's first posting was aboard the USS Icarus, however, later canon sources revealed that her first posting was the Al-Batani.
Six months into the Arias Expedition, Admiral Paris and Janeway were in a shuttlecraft orbiting Utrea II, when they were captured by the Cardassian, Gul Camet. The two officers were rescued by Lt. Tighe, whose life was in turn saved by Janeway. As a result, Paris recommended that Janeway switch from science division to command division.
In 2358, Janeway lost both her fiance and father while they were testing the prototype ship Terra Nova on Tau Ceti Prime. While making a final approach for landing, the ship crashlanded on Tau Ceti into a polar icecap. While Kathryn survived the crash, the others were frozen to death. She was rescued and took a leave of absence to deal with her deep depression.
In 2359, Janeway returned to active duty and announced her intention to switch to the command division at Starfleet Headquarters. At the arrangement of Admiral Paris, Janeway spent six months on an Earth-bound assignment before being assigned a deep-space mission. While on Earth, she started to become closer to Mark Johnson.
In 2363, Captain Janeway assumed command of the USS Billings. The Billings was her first proper command, and she often felt deeply responsible for her actions and the effects on her crew. Following one away team mission, she felt deeply responsible for the loss of Ensign Yvonne Harper's legs, unborn child, and sanity(VOY episodes: "Revulsion" and "Night"; and novels: Pathways and Cloak and Dagger).
In 2365, the now Captain Janeway was in command of the USS Bonestell on a six-month exploratory mission of the Beta Quadrant. Following the mission, Janeway went before a review board consisting of Admiral Paris, Admiral McGeorge Finnegan, and Admiral Alynna Nechayev. Ensign Tuvok was called in to criticize Janeway's ignorance of tactical regulations on the mission, and it was recommended by Admiral Finnegan that Tuvok served under Janeway on her next deep-space mission. Janeway and Tuvok were still serving together on the Bonestell when Janeway asked Tuvok to transfer with her to Voyager.