The group say 1,100 animals were also seized or surrendered
The Irish Society for the Prevention of Cruelty to Animals (ISPCA) say more than 15,000 calls were made to its National Animal Cruelty Helpline last year.
It says this resulted in 3,000 investigations, 1,100 animals being seized or surrendered and 35 prosecutions.
The group has launched its Inspectorate Report for 2015, which details some of the most harrowing cases.
This included the discovery of a young lurcher dog in Wicklow, who had died from parvovirus. An inspection found the dog had not received any veterinary attention, resulting in a slow lingering death.
While a multi-agency investigation in Cork found 23 dogs living in squalid conditions and in varying degrees of neglect.
Most of the more than 3,000 investigations were working with pet owners to improve animal welfare concerns.
However, in some cases prosecutions were instigated under the Animal Health and Welfare Act, which came into force in March 2014.
The ISPCA say this legislation was "a huge step forward for animal welfare in Ireland".
"Not only does it demand higher standards of animal welfare and places a duty of care on animal owners, it also means the ISPCA is now uniquely placed to investigate allegations of cruelty to domestic animals and Inspectors can now report their findings directly to the Department of Agriculture as a prosecuting body."
The ISPCA has a total of eight authorised inspectors covering 17 counties and working with 19 affiliated member societies.
It also operates two rescue and rehabilitation centres - which were developed in to support rescue, rehabilitation and responsible re-homing of cruelly treated and neglected animals.
ISPCA chief inspector Conor Dowling said: "The report highlights the work of the ISPCA’s team of trained, professional Inspectors and focuses on ISPCA initiated prosecutions finalised in the courts in 2015.
"While our officers find a solution to most problems by working with animal owners, when serious instances of cruelty, neglect or abuse are uncovered we feel that those responsible should be held accountable in the courts."
The ISPCA is appealing to the public to keep supporting their efforts to stamp out animal cruelty, as each year it costs €1.4m to run its services. It says almost 90% of this comes from public donations.
Anyone who suspects animal cruelty or neglect can call the ISPCA National Animal Cruelty Helpline on 1890-515-515