He was 76 and is survived by his wife Aruna, a renowned social worker, and daughters Shefali and Suvarna, a relative told IANS.
Suffering from heart disease since long, he was rushed to the Sion Hospital on Sunday afternoon in a critical condition and admitted to the ICU there.
Sadhu, who was put on ventilator, was ailing with a muscular heart condition, cardio-myopathy, and breathed his last around 4.45 a.m. on Monday.
As per his last wish, there will be no funeral services and his body will be donated.
Born on June 17, 1941, in Paratwada, Amravati district of eastern Maharashtra, Sadhu acquired his B.Sc. degree from Nagpur University in 1961.
In his journalistic career spanning over four decades since 1962, he started as a freelancer and later worked with Times of India, Indian Express, Statesman and Kesari before taking over as editor of the Free Press Journal (1987-1989), besides writing for or heading several other Marathi publications.
For six years, he was also Professor and head of Department of Journalism of University of Pune till 2001, and earlier visited the US, France and Afghanistan to participate in media-literary events.
Sadhu strode the world of both journalism and literature with flair and wrote in Marathi, English and Hindi on news stories, edits, articles, short stories and novels, folk writings, translations of renowned literary works and various issues of international importance.
He shot to prominence with his first Marathi novel, "Mumbai Dinank" (Mumbai Dateline - 1973) and later his political blockbuster book, "Simhasan" (The Throne - 1977) which was adapted into an acclaimed Marathi film by Jabbar Patel with scripting by Vijay Tendulkar.
The film -- viewing the struggle for the post of Maharashtra Chief Minister from the eyes of a journalist and discussing the mafia-politician nexus in the 1970s -- is often listed among the best Marathi films in its genre and had achieved peaks of popularity after its release in 1979.
Later came Sadhu's musical play "Padgham" (Drumbeats - 1985), which was adapted and directed into a grand stage presentation by Jabbar Patel's Theatre Akademi.
In 2000, he co-scripted the film "Dr. Babasaheb Ambedkar" along with Sooni Taraporevala and Daya Pawar.
Through his writings encompassing a wide range of topics -- crime, politics, the lives and struggles of ordinary mortals in complex societies, revolutions, caste systems, human relations vis-a-vis technology and the like -- Sadhu explored in a humane manner the rich-poor, rural-urban and caste divides.
Over the years, he was conferred several honours, including the Bharatiya Bhasha Parishad Rachana Award (2009), Kaumi Ekta Foundation Award, New Delhi, Kolkata, and N.C. Kelkar Award, Acharya Atre Award, and Padmashri Vitthalrao Vikhe Patil Award for Lifetime Achievements in Literature, all Maharashtra.
In a prestigious honour, Sadhu was elected President of the 80th Akhil Bharatiya Marathi Sahitya Sammelan held in Nagpur, 2007.
Among his other major works include novels: Maharashtra; Kakasaheb Gadgil; Fidel, Che Ani Kranti; Ani Dragon Jaga Jhalya; Dragon Jaga Jhalyawar; Mukhawta; Shodhyatra; Sfot; Bahishkrit; Trishanku and Tisri Kranti.
His short stories comprise: Manoos Udto Tyaachi Gosht; Mukti; Mantrajagar; and Ziprya, among other collections.
Chief Minister Devendra Fadnavis, Maharashtra Congress President Ashok Chavan, members of the top literary and media fraternity recalled his services to journalism and literature, and mourned the demise of Sadhu.
A large number of people from various walks of life paid homage to Sadhu at his Bandra residence in the afternoon before his body was donated.
There were host of people who paid tribute to Sadhu. Many of them expressed their condolences on Twitter that can be read below:
— ABP News (@abpnewstv) September 25, 2017
My condolences to the family members of Arun Sadhuji.
Very few are equally proficient in both journalism and literature.#RIP #ArunSadhu pic.twitter.com/Knp2xLdXL3
— Praful Patel (@praful_patel) September 25, 2017
Very sad to know passing away of Noted Journalist and Writer #Arun Sadhu,his contribution will be remembered Condolences RIP
— Suresh Prabhu (@sureshpprabhu) September 25, 2017
Sad to hear the passing of senior journalist Arun Sadhu ji. My condolences to members of his family. @PTI_News
— Nawab Malik (@nawabmalikncp) September 25, 2017
Deeply saddened to know the demise of Legendary author in Marathi- Arun Sadhu????I have been a true admirer of his works! RIP ???? #ArunSadhu pic.twitter.com/Ve1EklkPCr
— sonalikulkarni (@sonalikulkarni) September 25, 2017
RIP #ArunSadhu , one of the best writer journalist this state ever witnessed. pic.twitter.com/Xh63vFPolu
— Akshay Bardapurkar (@akshayent) September 25, 2017
Saddened to hear about demise of senior journalist and writer Shri Arun Sadhu ji. May his soul rest in peace. @PTI_News
— sachin ahir (@AhirsachinAhir) September 25, 2017
ज्येष्ठ साहित्यिक, पत्रकार अरुण साधू यांचे निधन ...#सिंहासन #ArunSadhu भावपूर्ण श्रद्धांजली
— Dr.Jitendra Awhad (@Awhadspeaks) September 25, 2017
Maharashtra grieves the profound loss of Arun Sadhu, who straddled the worlds of literature and journalism with equal elan. RIP, Arun ji!
— Vinod Tawde (@TawdeVinod) September 25, 2017