Around 14:30, Hara informed Takagi that only 24 Zeros, eight dive bombers, and four torpedo planes from the carriers were working. Takagi was worried about his ships' fuel levels; his cruisers were at 50% and some of his destroyers were as low as 20%. At 15:00 Takagi said he had sunk two American carriers – "Yorktown" and a "-class". Inoue called the invasion convoy to Rabaul, postponed "MO" to 3 July, and ordered his forces to gather northeast of the Solomons to begin the "RY" operation.
"Zuikaku" and her escorts turned towards Rabaul while "Shōkaku" headed for Japan.
Aboard "Lexington", an explosion killed 25 men and started a large fire. Around 14:42, another large explosion occurred, starting a second fire. A third explosion occurred at 15:25. "Lexington"s crew began abandoning ship at 17:07. After the carrier's survivors were rescued, including Fitch and the carrier's captain, Frederick C. Sherman, at 19:15 the destroyer fired five torpedoes into the burning ship, which sank in 2,400 fathoms at 19:52 ().
Two hundred and sixteen of the carrier's 2,951-man crew sunk with the ship, along with 36 aircraft. "Phelps" and the other warships left to rejoin "Yorktown", which departed at 16:01, and TF17 moved to the southwest. Later that evening, MacArthur informed Fletcher that eight of his B-17s had attacked the invasion convoy and that it was moving to the northwest.
That evening, Crace sent "Hobart", which was low on fuel, and the destroyer , which was having engine trouble, to Townsville. Crace remained on patrol in the Coral Sea in case the Japanese invasion force tried to go towards Port Moresby.
The battle was the first naval battle in history in which the ships never saw or fired directly at each other. Instead, aircraft were used to attack each other.
This was a carrier-versus-carrier battle. Neither commander had experience with this. The commanders had poor communications. This was hard, because the battle took place over a large area. The planes flew so fast that it meant there was not much time to make decisions.
The Japanese had problems because Inoue was too far away at Rabaul to direct his naval forces. Fletcher was on a carrier, so it was easier for him to direct his forces. The Japanese admirals did not share information quickly.
The experienced Japanese carrier aircrews did better than those of the U.S. The Japanese aircrews did more damage with the same number of aircraft. The Japanese attack on the American carriers on 8 May was better organized than the U.S. attack on the Japanese carriers.
The Japanese had much higher losses to their carrier aircrews. They lost ninety aircrew killed in the battle compared with thirty-five for the Americans. Japan's highly skilled carrier aircrews could not be replaced because the training programs could not produce enough new aircrew. There were not training programs to produce skilled pilots. Coral Sea was the start of Japan losing its experienced aircrews.
The Americans did learn from their mistakes in the battle. They made improvements to their carrier fighting approach. The Americans improved their anti-aircraft defences. Radar gave the Americans an advantage in this battle.
Following the loss of "Lexington", improved methods for carrying airplane fuel and better ways of dealing with damage were developed by the Americans. Coordination between the Allied land-based air forces and the U.S. Navy was poor during this battle.
Japanese and U.S. carriers would fight again in the battles of Midway, the Eastern Solomons, and the Santa Cruz Islands in 1942, and the Philippine Sea in 1944. Each of these battles had an impact on what would happen in the Pacific War.
Both sides claimed victory after the battle. In terms of ships lost, the Japanese won a victory by sinking an American fleet carrier, an oiler, and a destroyer – . The Americans sunk a light carrier, a destroyer, and several smaller warships – . "Lexington" was one quarter of U.S. carrier strength in the Pacific. The Japanese public was told it was a victory.
The Allies won because the sea invasion of Port Moresby was stopped. This meant that supply lines between the U.S. and Australia were protected. Although pulling "Yorktown" away from the Coral Sea was like giving the sea area to the Japanese, the Japanese stopped their invasion plans.
The battle was the first time that a Japanese invasion force was stopped. This improved the morale of the Allies. The Allies had been defeated by the Japanese during the first six months of the Pacific War.
Port Moresby was important to the Allies. The US Navy said that the damage it did to the Japanese was greater than what it really did.
The battle affected the planning of both sides. Without in New Guinea, the Allied advance would have been more difficult. For the Japanese, the battle was seen as a problem. The battle showed the Japanese that American were not that good in battle. The Japanese thought that future carrier attacks against the U.S. would be successful.
One of the most important effects of the Coral Sea battle was the loss of and .
Yamamoto wanted to use these carriers to battle American carriers at Midway ("Shōhō" was supposed to support the Japanese invasion ground forces). The Japanese thought that they sank two carriers in the Coral Sea, but this still left at least two more U.S. Navy carriers, "Enterprise" and "Hornet", which could fight at Midway.
American carriers had more planes than Japanese carriers. The US also had land-based aircraft at Midway. This meant that the Japanese did not have more planes at Midway. The Americans would have three carriers at Midway, because "Yorktown" could still sail, even with the damage from Coral Sea. The U.S. Navy was able to repair Yorktown at Pearl Harbor between 27 and 30 May so that she could fight in the battle.
At Midway, 's aircraft were important in sinking two Japanese carriers. "Yorktown" also took a lot of the Japanese air attacks at Midway which would have been directed at the other American carriers.
The Americans worked hard to get the maximum number of forces for Midway. The Japanese did not try to include "Zuikaku" in the operation. The Japanese did not try to put the "Shōkaku" aircrews with "Zuikaku"s air groups or provide "Zuikaku" with new aircraft. "Shōkaku" had a damaged flight deck which required three months of repair in Japan.
Historians H. P. Willmott, Jonathan Parshall, and Anthony Tully think Yamamoto made an error in deciding support the "MO". Since Yamamoto thought the big battle with the Americans would be at Midway, he should not have sent fleet carriers to less important battle like "MO". Japanese naval forces were weakened at both the Coral Sea and Midway battles, which allowed the Allies to defeat them.
Yamamoto did not notice another thing about the Coral Sea battle. The Americans put their carriers the right place and time to fight the Japanese. U.S. Navy carrier aircrews showed skill and tried to do major damage to the Japanese carrier forces. Japan lost four fleet carriers at Midway, which made Japan start to lose the Pacific War.
The Australians and U.S. forces in Australia were disappointed with the Battle of the Coral Sea. They thought that the "MO" operation was going to lead to an invasion of the Australian mainland. In a meeting held in late May, the Australian Advisory War Council said the battle was disappointing since the Allies knew about the Japanese plans.
General MacArthur told Australian Prime Minister John Curtin that Japanese forces could attack anywhere if supported by the IJN.
Because of the losses in carriers at Midway, the Japanese were unable to invade Port Moresby from the sea. Japan tried to capture Port Moresby by land. Japan began its attack towards Port Moresby along the Kokoda Track on 21 July from Buna and Gona.