Signal Flare is the third upgrade on the second path for the Mortar Tower in Bloons TD 5. It costs $425 on Easy, $500 on Medium, $540 on Hard, and $600 on Impoppable. It allows the Mortar Tower to detect and attack Camo Bloons. In Bloons TD 5, the Mortar Tower cannot target camo bloons without this upgrade. When a bloon is struck by with this upgraded tower, the bloon loses its camo status and turns back into a normal or Regen Bloon (depending on its initial status). Towers without camo detection can attack the once-camo or once camo-regen bloons.
- This upgrade and the unupgraded Mortar Tower have the Monkey's fingers in its ears.
- This upgrade was the only upgrade that removed Camo bloon status from bloons, until the Monkey Engineer's Cleansing Foam upgrade in Bloons Tower Defense 5 Deluxe and the Monkey Sub's Submerge and Support upgrade and the Tier 4 upgrade for the Ice Fortress in Bloons TD 5 Mobile.
- It's the only 3rd Upgrade which is cheaper than the unupgraded Tower, unupgraded costing $750, Signal Flare costing $500.
- A x/3 Mortar Tower costs more than a 3/x Monkey Engineer, but is more effective in some cases.