Nadia is one of the main characters found in Metal Slug 4.
"This is suh-sweet, non?" - Nadia's pet phrase
Nadia dreamt of becoming a supermodel, but could not resist eating. She kept on eating and gaining weight. She then enlists in the Regular Army, despite her modelling manager's plea, to keep the weight down, and succeeds in doing so. However, she finds a true potential for being a soldier and transfers into the S.P.A.R.R.O.W.S to gain combat experience. The operation against the Amadeus Syndicate was her first combat assignment. When it all ended, she didn't want to leave her new exciting life, so she inscribed into the Regular Army's Secret Services to continue working as an agent.
Nadia plays the same as any other character, although she uses a high-voltage Taser as her melee attack. Due to an in-game bug, she earns less points when using it.
Nadia cameos in Metal Slug Defense in the game's POW list, but she finally becomes a playable unit in a later update. She uses her taser as a close range attack and a Heavy Machine Gun that shoots Vulcan ammo as her long range attack. Her special is deploying a Slug Crawler that starts on the base and crawls up to her. Once she's on the slug, it shoots Vulcan ammo as normal attacks and she throws a Molotov as her special.
In 1.42.0, a special version of Nadia wearing a Valentine's dress, called Valentine Nadia, appears as an event unit. Her taser is replaced with a chocolate covered whisk, and her special has her tossing various explosives disguised as chocolate boxes.
Nadia later reappears in Metal Slug Attack, which now re-establishes her and Trevor as part of the main cast. Units of her can be earned by the Daily Login or by the POW Shop. Her Valentine's Day form also shows up as part of the "Chocolate of the Dead" event as a pre-acquisition unit (now a Medal Crank unit), now able to toss a small batch of boxes as a counterattack. In the event's story, she's protecting her chocolate from a horde of zombified Tarmas and Trevors.
A new version of Nadia wearing a skin-tight spy suit is introduced in the "Code: Assault" event as a VIP Crank unit (now an Event Crank unit). She uses a new weapon called the Sub-machine Gun, calls a modified Slug Crawler, and tosses floating bombs as her special while on the slug. Special Nadia, as this version is called, makes no appearance in the event's story, although it's assumed she's on a mission to rescue MS-Alice from the Amadeus Syndicate before Dragunov and her troops take Alice away first.
Her zombified form has a new sound effect to mimic the ones used in Metal Slug 3 (she originally had an echoed scream rather than a gurgled one).
- The animation of Nadia eating a piece from a candy bar is unused in Metal Slug 4. It is restored in Metal Slug Defense and Metal Slug Attack.
- Tyra is a sprite edit of Nadia, who also is an edit of Eri.
- Nadia is the first female character in the series so far to have her own custom melee attack; the Stun Gun.
- After the events of Metal Slug 4, her (and Trevor's) whereabouts are unknown, as she has yet to make another appearance in the main series.