Tatyana Felgengauer, a 32-year-old presenter for Echo of Moscow, was attacked after the suspect entered the radio station's building in central Moscow and blinded the security guard with a spray, editor-in-chief Alexei Venediktov said.
"He then came with a knife and stabbed Tanya," Venediktov told reporters.
"There was a lot of blood and she was in shock," the editor said, adding that the attacker, who was overpowered by a security guard, had appeared to be aiming at her.
Ida Sharapova, another employee at the radio station, said the suspect grabbed Felgengauer before he stabbed her.
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"At first I thought he knew her," she told reporters.
The Investigative Committee, which probes serious crimes, said it has opened a criminal case against a 48-year-old man on suspicion of attempted murder.
Citing preliminary information, Moscow police said the attacker was driven by "personal animosity" and that he was a "citizen of a foreign country."
Venediktov said he was told "there was no threat to life but she is in a serious condition," adding that Felgengauer had been able to get out of the building on her own two feet.
He also said that two more people had been hurt: the security guard downstairs who had the substance thrown at his face and another guard upstairs who was able to pin the attacker down.
Radio station employee Vitaly Ruvinsky posted on Twitter a photo of the dishevelled man dressed in a black jacket and trousers seated in a chair.
Police officer Yury Titov said the suspect tried to hide in the building after he stabbed the journalist but was found by the security guards.
Venediktov said the man had a drawing of the office plan.
Guard Aleksandr Usachyov, who had overpowered the man, also said the man appeared to be targeting Felgengauer.
"I grabbed his knife and pinned him to the floor," he said.
Felgengauer is one of the radio station's deputy editors and a longtime presenter of a morning news programme.
She is also actively involved in opposition rallies and has thousands of followers on her public Facebook page.
The Echo of Moscow radio has been the mouthpiece of the country's liberal opposition since the Soviet era, with its editorial policy frequently putting it on political thin ice.
Since then the Echo of Moscow has come a long way, becoming one of the top-cited media in Russia and by far the most popular talk radio station, with broadcasting in many of the country's regions.
It is majority owned by Gazprom Media, the media arm of Russian natural gas giant Gazprom.
Russia has a disturbing record of attacks on journalists, with 58 killed since 1992, according to the Committee to Protect Journalists. Threats made against journalists often go unaddressed and attacks are not investigated.