She was extensively employed during World War II in conjunction with an aircraft carrier task force, or as part of a cruiser squadron with her sister ship, Tone.

Though the external dimensions were close to the Mogami class, the design was quite different, with four twin 203 mm (8-inch) main battery turrets placed forward of the bridge, the second super firing over the first, reserving the entire stern area as a large sea plane hangar.

At 0630, Tone and Chikuma each launched short range Nakajima E4N2 Type 90-2 Reconnaissance Seaplane to act as pickets and patrol south of the Striking Force.

During the subsequent attack, the battleships Arizona, Oklahoma, West Virginia and California were sunk and Nevada, Pennsylvania, Tennessee, Maryland and other smaller ships were damaged.

On 14 January 1942, CruDiv 8 was based out of Truk in the Caroline Islands, and covered the landings of Japanese troops at Rabaul, New Britain and attacks on Lae and Salamaua, New Guinea.

Chikuma and Tone later escorted carriers during the Raid on Port Darwin, Australia on 19 February, which sank 11 ships to air attacks.

Hits from Hiei, Tone and dive bombers from the aircraft carriers Sōryū and Akagi finally stopped Edsall, which was then finished off by Chikuma.

[5][6] On 4 March, Chikuma and the destroyer Urakaze located and sank the 5,421-ton Dutch merchant Enggano (which had earlier been damaged by a floatplane from the cruiser Takao).

After searching for more remnants of the Royal Navy, the Indian Ocean Task Force launched 91 Aichi D3A1 "Val" dive-bombers and 41 Mitsubishi A6M2 "Zeke" fighters on 9 April against the British naval base at Trincomalee, Ceylon.

On 4 June, Tone and Chikuma each launched two Aichi E13A1 "Jake" long-range reconnaissance floatplanes to search out 300 miles (480 km) for American carriers.

With the US invasion of Guadalcanal, Chikuma and Tone were ordered south again on 16 August with the aircraft carriers Shōkaku, Zuikaku, Zuihō, Jun'yō, Hiyō and Ryūjō.

However, a second floatplane was more successful, and the Japanese launched an attack against Enterprise, hitting it with three bombs which set her wooden deck on fire.

Through October, Chikuma and Tone patrolled north of the Solomon Islands, waiting word of recapture of Henderson Field by the Japanese.

They located the American fleet, and Abe followed with an attack which sank Hornet and damaged the battleship South Dakota and cruiser San Juan.

Chikuma (escorted by the destroyers Urakaze and Tanikaze) returned to Truk for emergency repairs, and was then sent back to Kure with the damaged carrier Zuihō.

However, on 17 May, Chikuma and Tone were tasked to accompany the battleship Musashi back to Tokyo for the state funeral of Admiral Isoroku Yamamoto.

From July to November, Chikuma was engaged in making troop transport runs to Rabaul, and to patrols of the Marshall Islands in unsuccessful pursuit of the American fleet.

After ferrying army troops to Okinawa, Chikuma was reassigned back to Singapore in July, serving as flagship for CruDiv 4 while Atago was under repairs.

On 23 October 1944, Chikuma (with Kumano, Suzuya and Tone) sortied from Brunei towards the Philippines with Vice Admiral Takeo Kurita's First Mobile Striking Force.

In the Battle of the Sibuyan Sea the following day Musashi was sunk, the cruiser Myōkō was crippled and had to be towed to safety, while the battleships Nagato and Haruna received damage.

She managed to close to within 5 nmi (5.8 mi; 9.3 km) of the escort carrier USS Gambier Bay, and landed numerous hits with her 8-inch (203 mm) guns to her flight deck, lighting her ablaze.

Going off of older sources of the Battle off Samar, Gambier Bay's sinking is usually credited to Chikuma, as she was known to have fired on her when Gambier Bay received her fatal damage, most crucially a hit that flooded her engine room and left her speed dropping drastically until she was dead in the water, and caused catastrophic flooding, usually listed as an 8-inch cruiser shell, likely from Chikuma.

However, general consensus among naval historians has landed on the claim Gambier Bay's sinking should be credited to Yamato, largely ridding Chikuma of her former glory.

[11][12] Samuel B. Roberts emptied almost the entirety of her ammunition on Chikuma, and mostly out of ammo and completely out of torpedoes, the destroyer escort was later sunk by the battleship Kongō.